Replace README.txt with README.md
>>> [!note] Migrated issue
<!-- Drupal.org comment -->
<!-- Migrated from issue #3319914. -->
Reported by: [komalparmar](https://www.drupal.org/user/3697368)
Related to !1
>>>
<p>We could be using README.md instead of README.txt to make use of the nicer rendering via markdown.</p>
<p>Now that we've moved to GitLab, we should probably use Markdown instead of plain .txt files for our documentation</p>
issue