add plugin quickstart docs page

[savente93]

Issue addressed

Fixes #375

Explanation

This PR should be reviewed together with https://github.com/savente93/hydromt-plugin-template. Currently the docs are still lacking a bit, but a good start has been made.

Checklist

• Updated tests or added new tests
• Branch is up to date with main
• Tests & pre-commit hooks pass
• Updated documentation if needed
• Updated changelog.rst if needed

Additional Notes (optional)

Add any additional notes or information that may be helpful.

[savente93]

Fixes #464

[hboisgon]

Thanks for giving this a good start @savente93 ! I now wrote what I hope should be quite a complete guide on how to develop a plugin. It does quote some parts of the dev guide but I thought nice for users to have everything (with links!) in one place.

We discussed that there is not enough figures in our docs so I added 2 of them. If they are not nice or clear we can remove or adapt. The powerpoint version is in our sharepoint.

Maybe @DirkEilander you would like to have a look before merging? Else it is now good for me.

[DirkEilander]

Thanks for this huge effort and great contribution @savente93 and @hboisgon

• I've made one PR for the cookiecutter (which I believe has already been merged)
• The docs contain an amazing level of detail and information. I'm really happy you took the time to write this down. I think it could still benefit from some restructuring though by 1) moving some general aspects to elsewhere in model section of the user guide; and 2) splitting it into basic and advanced topics
• Some conventions would be good to discuss, see specific comments below.
• A lot of the comments are simple typos, you can select these and commit in a batch commit.

[savente93]

@hboisgon I tried to take care of as many issues as I could but there are a couple of comments that I'm not sure how to respond to. Could you take another look please?

[savente93]

@DirkEilander I've resolved your comments as best I could and also done some light editing. Could you take another look?

[DirkEilander]

@DirkEilander I've resolved your comments as best I could and also done some light editing. Could you take another look?

Thanks @savente93! I've done a final check and happy for it to be merged.
Let's await some feedback from new developers to see how we improve and whether for instance a notebook could help.