Accept metro bundler config as an argument.

Proposed change:

Accept a `--config` argument & pass it on to react native bundle command.

Example usage -
`react-native-bundle-visualizer --platform android --config metro+esbuild.config.js`

Why is this needed:
It'll be easier to view bundle sizes when testing out different configurations of metro config.

Ex:: Bundling with es-build /without es-build.