Fix issues with vanilla vim

When TERM is not xterm-256color (for example in st or tmux) t_8f and
t_8b have to be set manually for colors to work.
Add XDG_CONFIG_HOME/vim to packpath so that plugins work.

.config/vim/xdg.vim

@@ -42,4 +42,6 @@ set runtimepath-=~/.vim
 set runtimepath^=$XDG_CONFIG_HOME/vim
 set runtimepath-=~/.vim/after
 set runtimepath+=$XDG_CONFIG_HOME/vim/after
+set packpath-=~/.vim
+set packpath^=$XDG_CONFIG_HOME/vim
 source $XDG_CONFIG_HOME/vim/vimrc