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.
Add the LL(1) context-free grammar (GRAMMAR.ebnf), token and syntax
reference (SYNTAX.md), LL(1) verification tool (ll1_check.py), and a
fibonacci example demonstrating the language.
