Add bottom navigation bar item

forui/lib/src/widgets/bottom_navigation_bar/bottom_navigation_bar.dart

@@ -1,5 +1,11 @@
+import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 
+import 'package:meta/meta.dart';
+
+import 'package:forui/assets.dart';
+import 'package:forui/forui.dart';
+
 part 'bottom_navigation_bar_item.dart';
 
 class FBottomNavigationBar extends StatelessWidget {

forui/lib/src/widgets/bottom_navigation_bar/bottom_navigation_bar_item.dart

@@ -1,12 +1,161 @@
 part of 'bottom_navigation_bar.dart';
 
-class FBottomNavigationBarItem extends StatelessWidget {
-  const FBottomNavigationBarItem({super.key});
+class _FBottomNavigationBarWidget extends StatelessWidget {
+  final FBottomNavigationBarItem item;
+
+  final bool active;
+
+  const _FBottomNavigationBarWidget({
+    required this.item,
+    required this.active,
+    super.key,
+  });
 
   @override
   Widget build(BuildContext context) {
-    return const Placeholder();
+    final style = item.style!; // TODO: fix.
+
+    return MouseRegion(
+      cursor: SystemMouseCursors.click,
+      child: Column(
+        children: [
+          item.icon(
+            height: style.iconSize,
+            colorFilter: ColorFilter.mode(
+              active ? style.activeIconColor : style.inactiveIconColor,
+              BlendMode.srcIn,
+            ),
+          ),
+          Text(
+            item.label,
+            style: active ? style.activeTextStyle : style.inactiveTextStyle,
+          ),
+        ],
+      ),
+    );
+  }
+
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+    properties
+      ..add(DiagnosticsProperty('item', item))
+      ..add(FlagProperty('active', value: active, ifTrue: 'active'));
   }
 }
 
-class FBottomNavigationBarItemStyle {}
+/// A [FBottomNavigationBar] item.
+class FBottomNavigationBarItem {
+  /// The style.
+  final FBottomNavigationBarItemStyle? style;
+
+  /// The icon.
+  final SvgAsset icon;
+
+  /// The label.
+  final String label;
+
+  /// Creates a [FBottomNavigationBarItem].
+  const FBottomNavigationBarItem({
+    required this.icon,
+    required this.label,
+    this.style,
+  });
+}
+
+/// [FBottomNavigationBarItem]'s style.
+class FBottomNavigationBarItemStyle with Diagnosticable {
+  /// The icon's color when this item is active.
+  final Color activeIconColor;
+
+  /// The icon's color when this item is inactive.
+  final Color inactiveIconColor;
+
+  /// The icon's size. Defaults to `24`.
+  final double iconSize;
+
+  /// The text's style when this item is active.
+  final TextStyle activeTextStyle;
+
+  /// The text's style when this item is inactive.
+  final TextStyle inactiveTextStyle;
+
+  /// Creates a [FBottomNavigationBarItemStyle].
+  FBottomNavigationBarItemStyle({
+    required this.activeIconColor,
+    required this.inactiveIconColor,
+    required this.iconSize,
+    required this.activeTextStyle,
+    required this.inactiveTextStyle,
+  });
+
+  /// Creates a [FBottomNavigationBarItemStyle] that inherits its properties from the given [FColorScheme] and [FTypography].
+  FBottomNavigationBarItemStyle.inherit({required FColorScheme colorScheme, required FTypography typography})
+      : activeIconColor = colorScheme.primary,
+        inactiveIconColor = colorScheme.foreground.withOpacity(0.5),
+        iconSize = 24,
+        activeTextStyle = typography.sm.copyWith(color: colorScheme.primary),
+        inactiveTextStyle = typography.sm.copyWith(color: colorScheme.foreground.withOpacity(0.5));
+
+  /// Returns a copy of this [FBottomNavigationBarItemStyle] with the given properties replaced.
+  ///
+  /// ```dart
+  /// final style = FBottomNavigationBarItemStyle(
+  ///   activeIconColor: Colors.black,
+  ///   inactiveIconColor: Colors.white,
+  ///   ...
+  /// );
+  ///
+  /// final copy = style.copyWith(
+  ///   inactiveIconColor: Colors.blue,
+  /// );
+  ///
+  /// print(copy.activeIconColor); // black
+  /// print(copy.inactiveIconColor); // blue
+  /// ```
+  @useResult
+  FBottomNavigationBarItemStyle copyWith({
+    Color? activeIconColor,
+    Color? inactiveIconColor,
+    double? iconSize,
+    TextStyle? activeTextStyle,
+    TextStyle? inactiveTextStyle,
+  }) =>
+      FBottomNavigationBarItemStyle(
+        activeIconColor: activeIconColor ?? this.activeIconColor,
+        inactiveIconColor: inactiveIconColor ?? this.inactiveIconColor,
+        iconSize: iconSize ?? this.iconSize,
+        activeTextStyle: activeTextStyle ?? this.activeTextStyle,
+        inactiveTextStyle: inactiveTextStyle ?? this.inactiveTextStyle,
+      );
+
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+    properties
+      ..add(ColorProperty('activeIconColor', activeIconColor))
+      ..add(ColorProperty('inactiveIconColor', inactiveIconColor))
+      ..add(DiagnosticsProperty('iconSize', iconSize))
+      ..add(DiagnosticsProperty('activeTextStyle', activeTextStyle))
+      ..add(DiagnosticsProperty('inactiveTextStyle', inactiveTextStyle));
+  }
+
+  @override
+  bool operator ==(Object other) =>
+      identical(this, other) ||
+      other is FBottomNavigationBarItemStyle &&
+          runtimeType == other.runtimeType &&
+          activeIconColor == other.activeIconColor &&
+          inactiveIconColor == other.inactiveIconColor &&
+          iconSize == other.iconSize &&
+          activeTextStyle == other.activeTextStyle &&
+          inactiveTextStyle == other.inactiveTextStyle;
+
+  @override
+  int get hashCode =>
+      activeIconColor.hashCode ^
+      inactiveIconColor.hashCode ^
+      iconSize.hashCode ^
+      activeTextStyle.hashCode ^
+      inactiveTextStyle.hashCode;
+}