Make a list of contributing models

[Peter9192]

We now have https://github.com/WAM2layers/Moisture_tracking_intercomparison/blob/main/Contributing_models.md, but there's only 2 models listed there.

Another idea: it might be nice to add contact persons to each of the models. Then, if I have a question about one of the models, I could easily find someone to help me :-)

Notice that you can add nice tables in markdown like so:

|header | header |
|---|---|
|content|content|

Which renders as:

header	header
content	content