Major mode for editing Tengo code.
Tengo is a small, dynamic, fast, secure scripting language for Go.

Features:
- Syntax highlighting (keywords, builtins, functions, variables, operators, numbers)
- Context-aware indentation (ignores braces/parens/brackets in strings/comments)
- Comment handling (// and /* */)
- Imenu support (top-level functions and variables)
- Electric pairing
- Defun navigation (works for top-level, named, and nested/anonymous functions)

Based on https://github.com/geseq/tengo-vim and official Tengo docs.