Fix the relative links in the READMEs published to npmjs

PR Goal?

Relative links in our READMEs work correctly on GitHub, but not on npmjs. And unfortunately, there isn't a solution that will work on both, because github does some relative link rewrite on render than npmjs does not, and making it work on one site breaks it on the other.

So I decided to go for an automated post-edit option in our release workflow. It's not universal: if we add other relative links, we'll likely have to modify the release workflow again. But it's effective.

Fixes?

Fixes #311

Feedback sought?

sanity checking

Priority?

before the next minor release

Tests added?

can't automate, but I exercised the code by pushing test tags (which I'll delete shortly)

How to test?

See workflow https://github.com/ReadAlongs/Studio-Web/actions/runs/9451153166/job/26031422594 displaying the links correctly in the "show the updated readmes" step.

Confidence?

High

Version change?

patch bump, since we can't update the readme for a version that's already published

We should publish the next patch soonish, so that our default version on npmjs has working links, but it's not urgent

ReadAlongs / Studio-Web