Add/Show/Delete Emojis on Notes (#181)

This MR adds the ability to view, add, and delete emojis from notes and comments.

This action can be performed by default with the `Ea` (emoji add) keybinding, and the `Ed` (emoji delete) keybinding. Only emojis added by the current user are eligible for deletion. The MR also implements a popup functionality which shows the user who added emojis on hover.

Implements #179

lua/gitlab/hover.lua

@@ -0,0 +1,78 @@
+local M = {}
+
+M.show_popup = function(char)
+  -- Close existing popup if it's open
+  if M.popup_win_id and vim.api.nvim_win_is_valid(M.popup_win_id) then
+    vim.api.nvim_win_close(M.popup_win_id, true)
+  end
+
+  -- Create a buffer for the popup window
+  local buf = vim.api.nvim_create_buf(false, true)
+
+  -- Set the content of the popup buffer to the character
+  vim.api.nvim_buf_set_lines(buf, 0, -1, false, { char })
+
+  -- Define the popup window options
+  local opts = {
+    relative = "cursor",
+    row = -2,
+    col = 0,
+    width = 2, -- Width set to 2 to accommodate the border
+    height = 1,
+    style = "minimal",
+    border = "single",
+  }
+
+  -- Open the popup window and store its ID
+  M.popup_win_id = vim.api.nvim_open_win(buf, false, opts)
+end
+
+M.close_popup = function()
+  if M.popup_win_id and vim.api.nvim_win_is_valid(M.popup_win_id) then
+    vim.api.nvim_win_close(M.popup_win_id, true)
+    M.popup_win_id = nil -- Reset the window ID
+  end
+end
+
+M.init = function()
+  -- Set up autocommands
+  vim.api.nvim_create_autocmd({ "CursorHold" }, {
+    callback = function()
+      -- Get the current cursor position
+      local row, col = unpack(vim.api.nvim_win_get_cursor(0))
+      row = row - 1 -- Adjust row because Lua is 1-indexed
+      col = col - 2 -- Adjust to account for > at front of line
+
+      if col < 1 then
+        return
+      end
+
+      -- Get the text of the current line
+      local line = vim.api.nvim_buf_get_lines(0, row, row + 1, false)[1]
+
+      -- Correctly handle multi-byte characters, such as emojis
+      local byteIndexStart = vim.str_byteindex(line, col)
+      local byteIndexEnd = vim.str_byteindex(line, col + 1)
+
+      -- Extract the character (or emoji) under the cursor
+      local char = line:sub(byteIndexStart + 1, byteIndexEnd)
+
+      -- Proceed only if char is not empty (to avoid empty popups)
+      if char == "" then
+        return
+      end
+
+      M.show_popup(char)
+    end,
+    buffer = vim.api.nvim_get_current_buf(),
+  })
+
+  vim.api.nvim_create_autocmd({ "CursorMoved", "CursorMovedI" }, {
+    callback = function()
+      M.close_popup()
+    end,
+    buffer = vim.api.nvim_get_current_buf(),
+  })
+end
+
+return M