CLI improvements

[FeodorFitsner]

• --verbose flag - verbose output.
• --mobile flag - (removes .so) from app dest archive.
• --web flag for packaging for pyodide.
• --find-links option for installing pip dependencies from alternative sources (indexes).
• --dep-mappings for rewriting flet dependency to either flet-embed or flet-pyodide.
• --req-deps for adding required dependencies like flet-embed or flet-pyodide.
• --platform option for use with sitecustomize.py to tweak pip to pull platform-specific packages.
• More structured regular output.
• Bump deps versions (Close #39).