feat: add initial project scaffold with lexer, parser, tokenizer, and example source

Add the foundational source files for the Wren language implementation including the lexer (src/lexer.c, src/lexer.h), parser (src/parser.c, src/parser.h), token management (src/token.c, src/token.h), main entry point (src/main.c), a man page (src/wren.1), a .gitignore for build and Xcode artifacts, and a minimal example script (example/hello.wren). The lexer handles single-character tokens, names, numbers, strings, whitespace, and indentation; the parser implements a Pratt-style precedence climbing parser for expressions, blocks, and variable declarations; the token module provides doubly-linked list token storage and buffer management.

.gitignore

@@ -0,0 +1,5 @@
+# Output directory.
+build/
+
+# XCode user-specific stuff.
+xcuserdata/