Add documentation to a number of components in the production pipeline package

[kaitejohnson]

Problem

There are a number of functions/components in the cfaforecastrenewalww package that are missing documentation. Some of this will be replaced by documentation in the modeling package, but the remainder that is in use still will need improved documentation. This includes:

• flusight_location_table package data
• most parts of pre_processing.R (which will be replaced with lots of functionality from wweval
• parts of get_data.R
• parts of plots.R
• parts of process_model_outputs.R
• delay_distribs.R

Requirements

• [ ] sufficient documenation for an internal user to understand the pipeline.
• [ ] all documentation should have type notes for function arguments and outputs