Convert vim config to XDG standard

https://blog.joren.ga/configuring/vim-xdg

vim/.config/profile/env.d/vim.env

@@ -0,0 +1,3 @@
+# shellcheck disable=SC2016,SC2034
+VIMINIT='if !has("nvim") | source $XDG_CONFIG_HOME/vim/vimrc | endif'
+MYVIMRC='$XDG_CONFIG_HOME/vim/vimrc'

vim/.config/vim/init.d/xdg.vim

@@ -0,0 +1,21 @@
+if empty($MYVIMRC) | let $MYVIMRC = expand('%:p') | endif
+
+if empty($XDG_CACHE_HOME)  | let $XDG_CACHE_HOME  = $HOME.'/.cache'       | endif
+if empty($XDG_CONFIG_HOME) | let $XDG_CONFIG_HOME = $HOME.'/.config'      | endif
+if empty($XDG_DATA_HOME)   | let $XDG_DATA_HOME   = $HOME.'/.local/share' | endif
+
+set runtimepath^=$XDG_CONFIG_HOME/vim
+set runtimepath+=$XDG_CONFIG_HOME/vim/after
+set runtimepath+=$XDG_DATA_HOME/vim
+
+set packpath^=$XDG_DATA_HOME/vim
+call mkdir($XDG_DATA_HOME.'/vim/spell', 'p', 0700)
+
+set backupdir=$XDG_CACHE_HOME/vim/backup | call mkdir(&backupdir, 'p', 0700)
+set directory=$XDG_CACHE_HOME/vim/swap   | call mkdir(&directory, 'p', 0700)
+set undodir=$XDG_CACHE_HOME/vim/undo     | call mkdir(&undodir,   'p', 0700)
+set viewdir=$XDG_CACHE_HOME/vim/view     | call mkdir(&viewdir,   'p', 0700)
+
+if !has('nvim')
+  set viminfofile=$XDG_CACHE_HOME/vim/viminfo
+endif

vim/.config/vim/vimrc

@@ -1,15 +1,15 @@
 " Load from init.d instead of plugin directory. This is done so a leader key
 " can be set before loading plugin settings. This allows the plugin setting
 " files to set mappings with leader keys
-for f in split(glob('~/.vim/init.d/*.vim'), '\n')
+for f in split(glob($XDG_CONFIG_HOME.'/vim/init.d/*.vim'), '\n')
     exe 'source' f
 endfor
 
 " The plugged plugin manager function calls need to be called between the
 " plug#begin and plug#end. Because of that, using the normal plugin directory
 " loading won't work.
-call plug#begin('~/.vim/plugged')
-for f in split(glob('~/.vim/plug.d/*.vim'), '\n')
+call plug#begin($XDG_DATA_HOME.'/vim/plugged')
+for f in split(glob($XDG_CONFIG_HOME.'/vim/plug.d/*.vim'), '\n')
     exe 'source' f
 endfor
 call plug#end()