feat: custom sets and VimBeGood

- added custom sets for line numbers (absolute in Insert, relative in Normal)
- added VimBeGood plugin

lua/custom/plugins/init.lua

@@ -2,4 +2,6 @@
 --  I promise not to create any merge conflicts in this directory :)
 --
 -- See the kickstart.nvim README for more information
-return {}
+return {
+	'ThePrimeagen/vim-be-good'
+}