Imports https://github.com/dnfield/vector_graphics into this repository,
with history, and updates it to follow repository conventions:
- Adds missing licence headers.
- Removes analysis options and fixes resulting warnings.
- Updates min SDKs.
- Autoformats.
- Updates pubspecs to follow repo standard, including updating the
metadata
  to point to the Flutter repositories.
- Allows `xml` as a pinned dependency, and relaxes the pinning
requirement
  in the repo tools to allow an explicit, inclusive-endpoint range.
- Skips some unit tests on unsupported platforms.
- Adds repo metadata.
- Bumps versions and slightly relax version constraints to allow the new
  versions.