Suggestion / chore: add repo description, topics, website link

[andypiper]

It might be an idea to add some more metadata to the repo main page:

• description
• topics (e.g. zxspectrum, esp32, platformio, etc)
• link to website -> may lead more people to buy via CS

[andypiper]

Also TODO work on community standards (CoC, Contribution guidelines, issue templates)

[cgreening]

✅ description
✅ topics (e.g. zxspectrum, esp32, platformio, etc)
✅ link to website -> may lead more people to buy via CS

Will work on the remainder.