Implement code documentation

[Cmdrd]

While the code base is relatively small, it has taken some time to get up to speed with the functionality, especially with not being as familiar with the provided Prometheus Python library metric functions.

Putting this issue in as a working thread for further documentation discussions.

Currently have a local branch for adding documentation but definitely throw suggestions in here. Will get a PR done for an initial evaluation.

[Cmdrd]

Also might be a good idea to document the metrics that are being returned, either in the README or somewhere else so that it is easier for someone to find what metrics they are looking for. A separate issue could be created for implementing that if there is interest in something like that.

[GollyTicker]

Having some basic documentation regarding the test and docker build process would also be good. (See #72). What do you think?

Otherwise people need to reverse-engineer it from the github workflow - and some may not be knowledgeable enough to look there in the first place...