Feat: save popup contents to register (#163)

Users can now provide a backup register when creating comments, notes, and so forth which will automatically be populated with the contents of the buffer prior to submission to Gitlab. This ensures that even if the API call fails the contents of the buffer is saved, which prevents the user from losing their changes. This is a MINOR update.

lua/gitlab/state.lua

@@ -35,6 +35,7 @@ M.settings = {
     help = nil,
     pipeline = nil,
     squash_message = nil,
+    backup_register = nil,
   },
   discussion_tree = {
     auto_open = true,
@@ -273,6 +274,9 @@ M.set_popup_keymaps = function(popup, action, linewise_action, opts)
   if action ~= nil then
     vim.keymap.set("n", M.settings.popup.perform_action, function()
       local text = u.get_buffer_text(popup.bufnr)
+      if M.settings.popup.backup_register ~= nil then
+        vim.cmd("0,$yank " .. M.settings.popup.backup_register)
+      end
       if opts.action_before_close then
         action(text, popup.bufnr)
         exit(popup, opts)