Add examples to documentation for running with UT, and emulating HLT1,2 & sprucing without UT on expected24 MC

This MR adds two new pages to the documentation, which link to (with minimal description) examples showing how to:

• Emulate the whole trigger chain on expected-24 signal MC whilst we wait for central MC productions with trigger included,
• Run with the expected with-UT configuration

Docs can be found at https://rjhunter-docs.web.cern.ch/

TODO:

• Put docs somewhere
• Fix doc build again -> Rec!3837 (merged); independent of this MR
• Add tests? Probs not for speed- might need to follow-up.