vim:ftplugin:vim: Use local <buffer> autocmd

Fix the issue that the vim config would always be reloaded on save
(jumping to the BOF; another TODO) even in non `*.vim` buffers, after a
vim file was opened once in the session.

Fix this by defining the autocmd only local to the current buffer.

See also :help autocmd-buflocal

.config/vim/ftplugin/vim.vim

@@ -2,5 +2,5 @@
 " Group to avoid "exponential" reloading. See:
 " https://stackoverflow.com/questions/2400264/is-it-possible-to-apply-vim-configurations-without-restarting
 augroup vimrc_reload
-	autocmd! BufWritePost * source $MYVIMRC | echom "Reloaded" | redraw
+	autocmd! BufWritePost <buffer> source $MYVIMRC | echom "Reloaded" | redraw
 augroup END