clip: Document edge cases

[m-mohr]

Process ID: clip

Describe the issue:

During the test suite creation, I identified that the clip process doesn't mention what happens if min > max for example.

Proposed solution:
We should check the tests and document what's missing, e.g. throw an error if min > max? Check what similar processes do, e.g. between.

Additional context:
Tests in #468

[m-mohr]

What have backends impemented? @soxofaan @guss84 @clausmichele @LukeWeidenwalker

[clausmichele]

In the xarray/dask implementation, if max < min, no error is raised. The base function is provided by numpy, and they explicitly mention this in the docs:
No check is performed to ensure a_min < a_max.

Anyway, we can agree to raise a predefined error if this happens.

[soxofaan]

I don't think we have a check either.
Specifying to throw an error makes most sense to me too

[m-mohr]

PR: #477