Add description and epilog to Synthesis b0

[frheault]

Quick description

Add a short description and a reference to the synb0 script. ...

Type of change

Check the relevant options.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Provide data, screenshots, command line to test (if relevant)

...

Checklist

• [ ] My code follows the style guidelines of this project (run autopep8)
• [ ] I added relevant citations to scripts, modules and functions docstrings and descriptions
• [ ] I have performed a self-review of my code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ ] I moved all functions from the script file (except the argparser and main) to scilpy modules
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 66.95%. Comparing base (1d8d122) to head (6a937d7).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #949 +/- ## ======================================= Coverage 66.95% 66.95% ======================================= Files 392 392 Lines 21037 21037 Branches 3197 3197 ======================================= Hits 14086 14086 Misses 5656 5656 Partials 1295 1295 ``` | [Components](https://app.codecov.io/gh/scilus/scilpy/pull/949/components?src=pr&el=components&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scilus) | Coverage Δ | | |---|---|---| | [Scripts](https://app.codecov.io/gh/scilus/scilpy/pull/949/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scilus) | `68.07% <0.00%> (ø)` | | | [Library](https://app.codecov.io/gh/scilus/scilpy/pull/949/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scilus) | `65.15% <ø> (ø)` | |