Fixes #114

Description

add garden size estimate evaluation notebook

Instructions for Reviewer

to generate the notebook, ensure jupytext is installed and then run the following line in terminal:
jupytext --to notebook asf_heat_pump_suitability/analysis/garden_size_estimates/20250106_evaluate_garden_size_estimates.py

Please pay special attention to ...
Please could you provide some feedback on this analysis. Namely:

• Do you think the selection criteria are appropriate and applied in the correct order?
• Have I accounted for the appropriate corrections to make this a fair analysis (e.g. applying weights, checking weights add to at least 0.9 etc.)
• Are there any suggestions you have to make the analysis more robust or accurate?
• Have the weights been applied correctly?
• Is there anything we should add to the analysis?

Checklist:

• I have refactored my code out from notebooks/
• I have checked the code runs
• I have tested the code
• I have run pre-commit and addressed any issues not automatically fixed
• I have merged any new changes from dev
• I have documented the code
  • Major functions have docstrings
  • Appropriate information has been added to READMEs
• I have explained this PR above
• I have requested a code review