Fix README tabs and link to blog post

This release merely updates the README.md to cater for the GitHub Actions Marketplace displaying tabs in an unhelpful way. It also links to the blog post about this.

Full Changelog: v0.1.0...v0.1.1

Schemar initial release

What's Changed

• feat: initial implementation by @johnnyreilly in #1

New Contributors

• @johnnyreilly made their first contribution in #1

Full Changelog: https://github.com/johnnyreilly/schemar/commits/v0.1.0