Missing vale documentation.

The vale linter available for many file types (e.g. asciidoc, markdown, etc.) lacks any form of documentation. It would be good to add proper documentation similar to how is done for other tools that also support multiple filetyles like cspell and write-good.

Also add a note in the documentation explaining how the glob patterns used to configure vale may affect ALEs output that uses temporary files that most probably won't match any glob pattern other than "*" (see: https://github.com/dense-analysis/ale/issues/3363#issuecomment-1046067503).