v1.8.3: Improve "word" experience in vscode. (#225)

The model (form language-configuration.json) accepts '-' as long as it
is surrounded by '\w'.

However, the editor still uses '-' as word boundary. This combination
sounds counter-intuitive, but works okish with highlighting: the
model is used to find the initial word, and the editor then finds
"whole" words by using the separators. This means that `--foo-bar` finds
other `foo-bar`s (and, more importantly, `foo-bar` also finds
`--foo-bar`). However, it also means that `foo-bar-gee` will now also be
highlighted for the `foo-bar` part.

A correct solution will use the LSP, which can provide a good list of
the identifiers that are relevant. (Initially maybe just all
identifiers that would match).