Archive the old Clock-Signal repository and direct users to this one

[ryandesign]

I just noticed what looks like an older repository for the Clock Signal project at https://github.com/TomHarte/Clock-Signal. You haven't committed over there since 2015, and you started this CLK repository six months later. There is an unanswered bug report over there from 2020 wondering if the project is still active. At that time, you were actively developing it over here.

It might help users who come across the old repository discover that the project is still active if you edit that old repository's description and its README.md to direct users over here. You can then close the old repository's open issues and mark the repository as archived to prevent further confusion.