[Feature] Add share "Share on Mastodon" to exercise-finished readme template

[FidelusAleksander]

copied from skills/introduction-to-github#1963 by @hejjoe

Summary

In the final step I can "Show off your new skills and inspire others!" - follow by links to X, bluesky and linkedin. Sadly a link to mastodon - which is also used by github - is missing.

Changes

Next to the buttons "share to X, "share to bluesky" and "share to linkedin" there should be a "share to mastodon" button.

Additional context

There are some projects with a share button on github.
https://github.com/codesyntax/mastodon-share-button
https://github.com/codepo8/mastodon-share

[FidelusAleksander]

Hey @hejjoe

I've started to look at this, and I'm facing a dilemma..

The projects you shared are JS based, which is cool because they allow to pick the Mastodon instance to post to

However, with our buttons being posted in the repository README we don't have the JS convenience, only Markdown and HTML. Unless I'm missing something, this means our button would have to point to one of the Mastodon instances.

Example:

This poses a question, does this even make sense, and if yes to which instance should the button point to?

1. mastodon.social
2. hachyderm.io
3. other?

Curious about your thoughts on this 💭