fix(nvcheatsheet): fix unicode highlighting and spacing of nvcheatsheet

As the nvim_buf_add_highlight and other functions use byte indexing instead
of character indexing, I have fixed the whitespace length to not include the
extra bytes of unicode and also for highlighting I had to get the correct byte
index for both text and space lines of cheatsheet using builtin functions.

Additional testing is required to see all cases are handled.
I have checked for emojis and glyphs working as of now.

fixes NvChad#74

lua/nvchad_ui/cheatsheet/grid.lua

@@ -54,8 +54,9 @@ return function()
       if type(mappings) == "table" then
         for keybind, mappingInfo in pairs(mappings) do
           if mappingInfo[2] then
-            column_width = column_width > #mappingInfo[2] + #prettify_Str(keybind) and column_width
-              or #mappingInfo[2] + #prettify_Str(keybind)
+            column_width = column_width > vim.fn.strdisplaywidth(mappingInfo[2] .. prettify_Str(keybind))
+                and column_width
+              or vim.fn.strdisplaywidth(mappingInfo[2] .. prettify_Str(keybind))
           end
         end
       end
@@ -78,12 +79,12 @@ return function()
     for mode, modeMappings in pairs(section) do
       local mode_suffix = (mode == "n" or mode == "plugin") and "" or string.format(" (%s) ", mode)
       local card_name = name .. mode_suffix
-      local padding_left = math.floor((column_width - #card_name) / 2)
+      local padding_left = math.floor((column_width - vim.fn.strdisplaywidth(card_name)) / 2)
 
       -- center the heading
       card_name = string.rep(" ", padding_left)
         .. card_name
-        .. string.rep(" ", column_width - #card_name - padding_left)
+        .. string.rep(" ", column_width - vim.fn.strdisplaywidth(card_name) - padding_left)
 
       card_headings[#card_headings + 1] = card_name
 
@@ -93,7 +94,7 @@ return function()
       if type(modeMappings) == "table" then
         for keystroke, mapping_info in pairs(modeMappings) do
           if mapping_info[2] then
-            local whitespace_len = column_width - 4 - #(prettify_Str(keystroke) .. mapping_info[2])
+            local whitespace_len = column_width - 4 - vim.fn.strdisplaywidth(prettify_Str(keystroke) .. mapping_info[2])
             local pretty_mapping = mapping_info[2] .. string.rep(" ", whitespace_len) .. prettify_Str(keystroke)
 
             cards[card_name][#cards[card_name] + 1] = "  " .. pretty_mapping .. "  "
@@ -242,8 +243,23 @@ return function()
 
         -- highlight mappings & one line after it
         elseif string.match(columns[column_i][i], "%s+") ~= columns[column_i][i] then
-          vim.api.nvim_buf_add_highlight(buf, nvcheatsheet, "NvChSection", i + #ascii_header - 1, col_start, col_end)
-          vim.api.nvim_buf_add_highlight(buf, nvcheatsheet, "NvChSection", i + #ascii_header, col_start, col_end)
+          local line = vim.api.nvim_buf_get_lines(buf, i + #ascii_header - 1, i + #ascii_header + 1, false)
+          vim.api.nvim_buf_add_highlight(
+            buf,
+            nvcheatsheet,
+            "NvChSection",
+            i + #ascii_header - 1,
+            vim.fn.stridx(line[1], columns[column_i][i], col_start),
+            vim.fn.stridx(line[1], columns[column_i][i], col_start) + vim.fn.strlen(columns[column_i][i])
+          )
+          vim.api.nvim_buf_add_highlight(
+            buf,
+            nvcheatsheet,
+            "NvChSection",
+            i + #ascii_header,
+            vim.fn.byteidx(line[2], col_start),
+            vim.fn.byteidx(line[2], col_start) + column_width
+          )
         end
       end
     end