Add support for metro js map in @rnx-kit/third-party-notices

[dannyvv]

Currently the third party notice generator assumes the js.map files are generated by webpack. This should be updated to support the Metro bundler as well. When metro is supported the defaults in the react-native cli should be updated to assume the bundle output of the project when no argument is given to make that use-case parameterless.

[tido64]

Correct me if I'm wrong but I thought the source map schema is universal? bundle-diff uses source maps to produce diffs and I used it to investigate Haul/Webpack vs Metro differences.

[tido64]

People have used @rnx-kit/third-party-notices with Metro without issues. Closing.