Introduce basic classes for regions of interest

[willGraham01]

Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?

A first step towards addressing #377 - introduces the low-level classes that we will need to represent these in the codebase.

As stated on the issue, we have to use wrapper classes since inheriting from shapely classes is problematic. This doesn't really matter too much though - if anything, it is rather helpful for separating the underlying (and rather counter-intuitive at times) shapely objects from the higher-level analysis functions that we're going to implement.

What does this PR do?

• Introduces the roi submodule, which contains a base class and two derived classes for representing RoIs.

References

#377

How has this PR been tested?

Addition of tests to the testing suite.
Docs successfully build.

Is this a breaking change?

No

Does this PR require an update to the documentation?

• Debated this, but decided we should hold off adding an example until we at least have some additional functionality to do something with these objects!

Checklist:

• The code has been tested locally
• Tests have been added to cover all new functionality
• The documentation has been updated to reflect any changes
• The code has been formatted with pre-commit