Communicate that feedback is welcome only but not PRs yet

[bencodezen]

• Feedback is welcome but no PRs at this moment since the docs team is still in progress with some sections

[bencodezen]

@phanan @NataliaTepluhina @sdras

At first, I thought maybe we'd put this message somewhere on the site, but maybe it'd be best just to add it as a PR template? Or maybe we should add some messaging somewhere that's like:

"Feedback welcome via GitHub issues, but please hold off on any pull requests as the docs are still in development and not ready for additional contributions."

[NataliaTepluhina]

@bencodezen I would add this to Contributing to docs section, PR template and also I would remove Edit on GitHub link for now from the Vuepress site