Add compound assignment operators (+=, -=, *=, /=, %=, &=, |=, ^=,
<<=, >>=) and shift operators (<<, >>) to the tmLanguage syntax
highlighting grammar. Patterns are ordered longest-first to prevent
shorter tokens from shadowing multi-character operators. Also update
fibonacci example to use += compound assignment.
Adds the vscode-flux extension with TextMate grammar covering keywords,
types, literals, operators, comments, and function/struct name highlighting.
Supports .flux and .flx file extensions.
