[nvim] fix comments and commentstring options in the nginx filetype

nvim/after/syntax/nginx.vim

@@ -0,0 +1,8 @@
+" Guess what. The `syntax/jinja.vim` script for the jinja templating language,
+" which is not included in neither Vim's runtime, nor Neovim's runtime, nor in
+" vim-polyglot (so the only way to get it is to install the python package) is
+" sourced in `syntax/nginx.vim` in vim-polyglot, which resets the `commentstring`
+" set in `ftplugin/nginx.vim` and sets `comments` to some garbage. This script
+" undoes that damage.
+let &l:comments = &g:comments
+let &l:commentstring = '# %s'