updated high level documentation

[benjaminleighton]

Hi @tomdurrant , I've done some automated analysis and semi automated edits to some of the high level documentation. I think this brings it more in line with the current capabilities of rompy. What do you think?

[tomdurrant]

HI @benjaminleighton - content looks good, but you are building these with references to xbeach, which is an external package. We can of course add it to the docs requirements, but we may want to think this through a little more. The options as I see them are

1. have all rompy docs combined into rompy-core (what this repo will ultimately become). Add all models as depdencies.
2. Have only core docs in here, and have model specific docs in a each respective repo
3. Some sort of dedicated docs repo.

We can probably leave that discussion until we are a bit further down the line of the model separation. For now, I suggest we remove xbeach references from the docs in this repo....?