Links on the public mps site at ravenbrook.com are unclear or not up to date

[thejayps]

"Read the Documentation" does not point to the current documentation hosted at readthedocs "Fork it on Github" presupposes that a visitor intends to fork the MPS. They might want to just look at the project.

[rptb1]

Partially resolved by Perforce changelist 199686 (see https://github.com/Ravenbrook/mps/pull/166#issuecomment-1772605138 ).

We could introduce further rewrite rules to resolve this further.