Move the glossary to the documentation

[leandro-lucarella-frequenz]

What's needed?

Now that we are generating the documentation as a website we should include the glossary there.

Proposed solution

Move https://github.com/frequenz-floss/frequenz-sdk-python/wiki/Glossary to docs/glossary.md or similar. It should probably be a top level page so it appears in the navigation bar on the top.

Use cases

No response

Alternatives and workarounds

No response

Additional context

No response