feat: change CTRL+b to use fzf

That allow us to fuzzy search for files in the buffer and preview its
content.

Author: Santiago Rodriguez

after/plugin/user_customizations.vim

@@ -2,6 +2,7 @@
 nmap <C-\> :Rg! <C-R><C-W><CR>
 nmap <C-/> :RG!<space><CR>
 nmap <C-p> :Files<CR>
+nmap <C-b> :Buffer<CR>
 
 " source user customizations if defined
 if filereadable(expand("~/.vimrc.after"))