Problem: filetype: Erlang lexical files are not recognized
Solution: Detect *.xrl files as leex filetype, include syntax and
filetype plugins (Jon Parise).
leex is the lexical analyzer generator for Erlang. Its input file format
follows a section-based structure and uses the `.xrl` file extension.
This initial work includes file detection, an ftplugin (which inherits
the Erlang configuration), and a syntax definition.
Reference:
- https://www.erlang.org/doc/apps/parsetools/leex.html
related: vim/vim#18819closes: vim/vim#18832b087c5452b
Co-authored-by: Jon Parise <jon@indelible.org>
