chore: add build-flatpaks docs

articles/en/build-flatpaks.md

@@ -0,0 +1,88 @@
+---
+Title: Build Flatpak(s) in Vanilla OS
+Description: Learn how to build Flatpak(s) in Vanilla OS.
+PublicationDate: 2024-09-31
+Listed: true
+Authors:
+    - mirkobrombin
+---
+
+Flatpak is a universal package format for Linux desktop applications. You can install them from the GNOME Software or using the command line. Optionally, you can also build them from source.
+
+## Requirements
+
+To build a Flatpak, you need to have the Flatpak Builder installed. You can install it with the following command:
+
+```bash
+flatpak install --user org.flatpak.Builder
+```
+
+This way the Flatpak Builder will be installed in the user space as a Flatpak itself.
+
+## Build a Flatpak
+
+First you need to clone the repository of the application you want to build or create your own [Flatpak manifest](https://docs.flatpak.org/en/latest/manifests.html). Then enter the root directory of the application and find the `org.example.Application.json` or `org.example.Application.yaml` file, also known as the manifest file. Inside the manifest file, you can find multiple fields that you can customize, such as the application ID, the runtime, the SDK, the sources, and the build options. Let's focus on the SDKs, extensions and base/runtime used to build the application, for example the following is the header of the Bottles manifest file:
+
+```yaml
+id: com.usebottles.bottles
+sdk: org.gnome.Sdk
+runtime: org.gnome.Platform
+base: org.winehq.Wine
+base-version: stable-23.08
+runtime-version: '46'
+command: bottles
+sdk-extensions:
+  - org.gnome.Sdk.Compat.i386
+  - org.freedesktop.Sdk.Extension.toolchain-i386
+```
+
+We need to install the runtime, the SDK, and the extensions used to build the application. For example, to install the runtime:
+
+```bash
+flatpak install --user org.gnome.Platform
+```
+
+this will show you the available versions of the runtime, choose the one you need according to the manifest file:
+
+```
+Looking for matches…
+Similar refs found for ‘org.gnome.Platform’ in remote ‘flathub’ (user):
+
+   1) runtime/org.gnome.Platform/x86_64/3.24
+   2) runtime/org.gnome.Platform/x86_64/3.26
+   3) runtime/org.gnome.Platform/x86_64/3.28
+   4) runtime/org.gnome.Platform/x86_64/3.30
+   5) runtime/org.gnome.Platform/x86_64/3.32
+   6) runtime/org.gnome.Platform/x86_64/3.34
+   7) runtime/org.gnome.Platform/x86_64/3.36
+   8) runtime/org.gnome.Platform/x86_64/3.38
+   9) runtime/org.gnome.Platform/x86_64/40
+  10) runtime/org.gnome.Platform/x86_64/41
+  11) runtime/org.gnome.Platform/x86_64/42
+  12) runtime/org.gnome.Platform/x86_64/43
+  13) runtime/org.gnome.Platform/x86_64/45
+  14) runtime/org.gnome.Platform/x86_64/44
+  15) runtime/org.gnome.Platform/x86_64/46
+
+Which do you want to use (0 to abort)? [0-15]:
+```
+
+which is the number `15` (GNOME 46). Then do the same for the SDK and the extensions.
+
+Finally, you can build the application with the following command:
+
+```bash
+flatpak-builder --user --install build-dir com.usebottles.bottles com.usebottles.bottles.yaml
+```
+
+where `build-dir` is the directory where the application will be built, `com.usebottles.bottles` is the application ID, and `com.usebottles.bottles.yaml` is the manifest file.
+
+## Run the application
+
+Once the application is built, you can run it with the following command:
+
+```bash
+flatpak run com.usebottles.bottles
+```
+
+or you can find it in the "Applications" menu.