Rewrite relative links when copying README

[backflip]

Following links from https://www.npmjs.com/package/@capsizecss/core sends me to 404 pages like https://github.com/seek-oss/capsize/blob/HEAD/packages/core/packages/metrics/README.md.

This PR extends the script copying the root's README to packages/core to rewrite relative links.

A local diff of the copied file (left: before, right: after):

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Latest commit: 289c319

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[michaeltaranto]

Are you able to extend this to find and replace link references too? e.g. like these

[michaeltaranto]

Thanks for opening this. It'd be good to extend the solution to cover link references which would also be broken.

[backflip]

Thanks for opening this. It'd be good to extend the solution to cover link references which would also be broken.

Good point. I have changed the replacement function to replace every occurrence of packages/EXISTING_PACKAGE/.