Forecast figure enhancements redux

[damonbayer]

Closes #167
Closes #331

Example figure:

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 92 lines in your changes missing coverage. Please review.

Project coverage is 24.32%. Comparing base (d8534e9) to head (8e3f92f).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
hewr/R/make_forecast_figure.R	0.00%	91 Missing ⚠️
pipelines/prep_data.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #349      +/-   ##
==========================================
- Coverage   25.30%   24.32%   -0.98%     
==========================================
  Files          22       22              
  Lines        1648     1714      +66     
==========================================
  Hits          417      417              
- Misses       1231     1297      +66     

Flag	Coverage Δ
hewr	37.44% <0.00%> (-4.24%)	⬇️
pipelines	5.15% <0.00%> (ø)
pyrenew_hew	27.96% <ø> (ø)

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[dylanhmorris]

LGTM, thanks!