Support syntax highlighting for glue string interpolation

[renkun-ken]

It should be possible to support glue string interpolation in the syntax file like other languages such as Python, JavaScript, and C#.

Also, it should also be possible to support language server features, as suggested at https://github.com/REditorSupport/languageserver/issues/601.

[jordantgh]

Hey, I'd be willing to take a look at this, any ideas where I could start? @renkun-ken