Add versioning information to repo documentation

[CEKrause]

The following decisions on versioning were made by project members. We need to add this to the repo documentation somewhere:

• WB polygons and csvs to be named by etc
• Versioning
  • Semantic versioning – major, minor and patch
  • Docker will be updated for all updates (m, m, p)
  • Patch – backwards compatible (e.g. add a new column, new data but the existing data doesn’t change, minor debugging)
  • Minor – incremental breaking changes (e.g. restructuring folders, deleting data, modifying schema)
  • Major – considerable updates we want to promote – changes + comms (e.g. any time we majorly change the polygons, if there’s a chance we can change analysis outputs).
• Single branch in DEA WB github page tagged with releases

[MatthewJA]

Note that the current version is currently stored in __version__.py; could probably update this to use setuptools_scm and automate some versioning.