Allow specifying dependency sun file name

## Summary - allow specifying an alternative project file name in `require` entries using `DIR:NAME` syntax - document new `require DIR:NAME` syntax ## Testing - `php Sun/vendor/Soup/build_lib.php` - `clang -o suncli Sun/sun.cpp -ISun/vendor/Soup Sun/vendor/Soup/libsoup.a -std=c++17 -fuse-ld=lld -lstdc++ -lstdc++fs -pthread` ------ https://chatgpt.com/codex/tasks/task_e_68b30893ba948325a6105375d295870d