clean: remove lua/kickstart and lua/custom directories

This commit also move health.lua from lua/kickstart/health.lua
into lua/health.lua

lua/custom/plugins/init.lua

@@ -1,8 +0,0 @@
--- You can add your own plugins here or in other files in this directory!
---  I promise not to create any merge conflicts in this directory :)
---
--- See the kickstart.nvim README for more information
-
----@module 'lazy'
----@type LazySpec
-return {}