Add download/open in Binder pre-amble for notebooks

[VeckoTheGecko]

If you want local copies of the notebooks, you can currently download them as a zip of them from our tutorials homepage https://docs.oceanparcels.org/en/latest/documentation/index.html . However:

• its unusual that someone would want to download all the notebooks (they probably just want to look at one of particular interest)
• this creating of the zip creates unnecessary complexity in the build process

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A better option would be to implement something similar to what xarray has on their gallery page - an autogenerated pre-amble (specified in conf.py) of

Here these are just links (no added complexity to the build process) and has the added benefit of providing a link directly to open in Binder and try the code.

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Needed changes:

• Add pre-amble (Binder link, and "download from GitHub" link)
  • Note: the link should not just point to main - but should depend on the version being built. This prevents downloading the latest notebook when an old version of docs is being looked at. Create a function _get_github_ref_for_build() which returns a GitHub reference/tag/branch name to be interpolated into the string (if "unknown" - e.g., running local - use main). Inspecting READTHEDOCS_VERSION_TYPE and READTHEDOCS_VERSION_NAME environment variables (docs) will help here.
• Remove zip building workflow

[erikvansebille]

Very good idea; I like it!

Does this also feed into the discussion about whether we serve the notebooks with or without outputs? I think that currently the outputs of the notebooks in v4-dev branch are trimmed? Or is that a different discussion?

[VeckoTheGecko]

Does this also feed into the discussion about whether we serve the notebooks with or without outputs?

I think that's a separate topic. IIRC at the moment the outputs are trimmed since that was easiest during v4 development. I think once we have a stable v4 we'll stop trimming again so that we can assert correctness via git diffs and so that the notebooks are visible on the site.

[nilodna]

I'm assigning myself on this one

[VeckoTheGecko]

Mildly tangental for @erikvansebille , I want to enable the RTD bot to comment things like

more info. You should have a request as admin of OceanParcels for this bot to be added to the repo