[nvim] Install telescope

Add these bindings:
- find_files to ,ff
- live_grep to ,fg
- buffers to ,fb
- help_tags to ,fh

config/nvim/init.lua

@@ -59,6 +59,7 @@ local keys = require 'keys'
 keys.init_key_opts()
 keys.init_window_key_mappings()
 keys.init_diagnostic_key_mappings()
+keys.init_telescope_mappings()
 
 local gui = require 'gui'
 gui.init()