Feat: Add Basic Lua Test Suite (#115)

This MR adds a Lua test suite to the project, run via busted, and introduces tests for a number of the utility functions. Subsequent work will have to be done to test functions that use the `vim.api` scope and external packages to the plugin.

lua/gitlab/actions/discussions.lua

@@ -892,7 +892,7 @@ end
 ---@param note Note
 ---@return string
 M.build_note_header = function(note)
-  return "@" .. note.author.username .. " " .. u.format_date(note.created_at)
+  return "@" .. note.author.username .. " " .. u.time_since(note.created_at)
 end
 
 M.build_note_body = function(note, resolve_info)
@@ -977,7 +977,7 @@ M.add_discussions_to_table = function(items)
     end
 
     -- Creates the first node in the discussion, and attaches children
-    local body = u.join_tables(root_text_nodes, discussion_children)
+    local body = u.spread(root_text_nodes, discussion_children)
     local root_node = NuiTree.Node({
       text = root_text,
       is_note = true,