Discussion sign and diagnostics (#78)

This MR adds support for in-line comments in the review pane. This allows you to view comments (as diagnostics) directly in the Neovim buffers that you are reviewing. You can then jump to them directly in the discussion tree if you want to reply, edit, and so forth.

lua/gitlab/actions/comment.lua

@@ -146,6 +146,7 @@ M.confirm_create_comment = function(text, range, unlinked)
   job.run_job("/comment", "POST", body, function(data)
     u.notify("Comment created!", vim.log.levels.INFO)
     discussions.add_discussion({ data = data, unlinked = false })
+    discussions.refresh_discussion_data()
   end)
 end