Revised Surface/HEEx/EEx Syntax
- Syntaxes: refactored Surface/HEEx/EEx with many improvements (thanks to @deathaxe).
- Themes: slightly darken the embed punctuation markers for Surface and (H)EEx tags.
- Elixir: allow digits in sigil string modifiers.
- Preferences: index Elixir
@attribute
definitions for "Goto Definition".