Update lists of operators/keywords in Julia and expand/refine highlighting

[jmert]

It appears the Julia highlighting rules have not recently been updated. To me it appears the current syntax definitions probably predate Julia v0.7, and much has changed since then. I was motivated in particular to fix parsing of the "broadcast expression" helper macro @. which currently isn't recognized, but once I got going, I made many other changes to try to bring the definition up to date.

I'd like to recognize @fredrikekre in particular for inspiring me to make changes here based on some of what he did for highlight.js (blog post and code branch).

Some of the more notable changes are:

• Updated keywords/builtins list from Julia v1.6 (currently at rc1) and greatly expanded set of operators/symbols which are recognized.
• Operator macros are recognized. In particular, the broadcast expression macro @. is now recognized as valid.
  • Unicode suffixes are handled in most contexts (such as infix +¹ or custom transpose 'ᵀ).
• Symbol literals are identified in simple contexts.
• Added command triple-quote expressions and special-cased raw"" strings which do not interpolate.
  • Non-standard string literals such as mystring"contents"suffix now identify their prefix/suffix as affixes.
• Type names in unambiguous contexts are highlighted as types. This necessarily can't catch everything (and hence there's still an explicit list of built-in types), but there are many places like type assertions/annotations and where expression where names can be highlighted with little chance of being wrong.
• The julia-repl highlighting alias is added to match Julia's own convention for use in Markdown documentation files.
• Tests for everything which was changed

[Anteru]

Merged, thanks a lot for this huge update!