Update README.md - How to report bugs or feedback

In README.md, update this phrase:

 First check if your issue wasn't already opened in gitlab.torproject.org, then file a trac ticket and choose the component: Webpages/Community.

to:

 First, check if the bug is already known. You can search and read all the issues at https://gitlab.torproject.org/. To create a new issue, please [request a new account](https://gitlab.onionize.space/) to access Tor Project's GitLab instance and [find the right repository](https://gitlab.torproject.org/tpo) to report your issue. Issues related to our websites should be filed under the [Web issue tracker](https://gitlab.torproject.org/groups/tpo/web/-/issues).