And load vimtex automatically. I discarded the autocommand as vimtex
only loads a small ftdetect script for tex and the rest of the plugin is
made up of ftplugins, indent files, etc. by itself.
The overhead of the autocmd feels bigger than just loading the small
component and letting vim doing the rest.
(But this is in now way tested/benchmarked. That is just how I feel and
it makes it a tad cleaner)
And move the plugin specific keybindings into 40-keybindings.vim.
`packloadall` sources the plugins directly in contrast to `packadd`.
Because of that we can access the `g:loaded_*` variables and do not have
to specify our own keybindings for vim-surround as now the user bindings
are loaded later and overwrite possible clashes.
