feat: add border for mason (#3080)

lua/lvim/core/mason.lua

@@ -3,6 +3,7 @@ local M = {}
 function M.config()
   lvim.builtin.mason = {
     ui = {
+      border = "rounded",
       keymaps = {
         toggle_package_expand = "<CR>",
         install_package = "i",