The project documentation is now hosted on GitHub pages. Pointing the documentation link to the documentation site home page will offer the reader easy access to the documentation for the latest and previous releases while also avoiding the maintenance burden of updating the readme on every release
Integrate old INSTALL into README.md, both files had a lot
of (potential) overlap.
Add template for new entries in NEWS, targetting next release.
Bump version number to 6.99-20211218
Tentatively, with the Github migration and all ongoing code
restructuring, we aim for a version 7.0 release at some point
in the future.