fix missing extend tag.

[arhimede]

Add markdown linting

[gsteel]

👍 on the article changes - Adding the markdownlint config file wont actually lint anything though will it? We'll need to add an action to CI that executes markdownlint-cli2 **/*.md

[arhimede]

👍 on the article changes - Adding the markdownlint config file wont actually lint anything though will it? We'll need to add an action to CI that executes markdownlint-cli2 **/*.md

yeah, i added the markdown linting config only to see if something is triggered
Currently only the readme.md is linted .
work in progress that linting part :-)