A largish release with many improvements and fixes from quite a few different contributors. Enjoy!

Deprecations:

• (chore) requireLanguage is deprecated.
  • Prefer getLanguage (with custom error handling) or built-time dependencies.
  • See Library API for more information.

Parser:

• enh(parser) use negative look-ahead for beginKeywords support (#2813) Josh Goebel
• enh(grammars) allow classNameAliases for more complex grammars Josh Goebel
• fix(vue): Language name now appears in CSS class (#2807) Michael Rush
• (chore) Clean up all regexs to be UTF-8 compliant/ready (#2759) Josh Goebel

New Languages:

• Added 3rd party Chapel grammar to SUPPORTED_LANGUAGES (#2806) Brad Chamberlain
• Added BBCode grammar to SUPPORTED_LANGUAGES (#2867) Paul Reid
• enh(javascript) Added node-repl for Node.js REPL sessions (#2792) Marat Nagayev

Language Improvements:

• enh(shell) Recognize prompts which contain tilde ~ (#2859) Guillaume Grossetie
• enh(shell) Add support for multiline commands with line continuation \ (#2861) Guillaume Grossetie
• enh(autodetect) Over 30+ improvements to auto-detect (#2745) Josh Goebel
  • 4-5% improvement in auto-detect against large sample set
  • properties, angelscript, lsl, javascript, n1ql, ocaml, ruby
  • protobuf, hy, scheme, crystal, yaml, r, vbscript, groovy
  • python, java, php, lisp, matlab, clojure, csharp, css
• fix(r) fixed keywords not properly spaced (#2852) Josh Goebel
• fix(javascript) fix potential catastrophic backtracking (#2852) Josh Goebel
• fix(livescript) fix potential catastrophic backtracking (#2852) Josh Goebel
• bug(xml) XML grammar was far too imprecise/fuzzy Josh Goebel
• enh(xml) Improve precision to prevent false auto-detect positives Josh Goebel
• fix(js/ts) Prevent for/while/if/switch from falsly matching as functions (#2803) Josh Goebel
• enh(julia) Update keyword lists for Julia 1.x (#2781) Fredrik Ekre
• enh(python) Match numeric literals per the language reference Richard Gibson
• enh(ruby) Match numeric literals per language documentation Richard Gibson
• enh(javascript) Match numeric literals per ECMA-262 spec Richard Gibson
• enh(java) Match numeric literals per Java Language Specification Richard Gibson
• enh(swift) Match numeric literals per language reference Richard Gibson
• enh(php) highlight variables (#2785) Taufik Nurrohman
• fix(python) Handle comments on decorators (#2804) Jonathan Sharpe
• enh(diff) improve highlighting of diff for git patches [Florian Bezdeka][]
• fix(llvm) lots of small improvements and fixes (#2830) Josh Goebel
• enh(mathematica) Rework entire implementation Patrick Scheibe
  • Correct matching of the many variations of Mathematica's numbers
  • Matching of named-characters aka special symbols like \[Gamma]
  • Updated list of version 12.1 built-in symbols
  • Matching of patterns, slots, message-names and braces
• fix(swift) Handle keywords that start with # Marcus Ortiz
• enh(swift) Match some keyword Marcus Ortiz
• enh(swift) Match @main attribute Marcus Ortiz

Dev Improvements:

• chore(dev) add theme picker to the tools/developer tool (#2770) Josh Goebel
• fix(dev) the Vue.js plugin no longer throws an exception when hljs is not in the global namespace Kyle Brown

New themes:

• StackOverflow Dark by Jan Pilzer
• StackOverflow Light by Jan Pilzer