(release) v0.5.3

[tomalrussell]

Follow these steps:

• Merge all desired PRs to main, let CI tests pass
• Update version number in pyproject.toml
• Push to main
• Start drafting a new release at https://github.com/nismod/snail/releases/new
  • Create a new tag: click "Choose a tag", enter new version number (e.g. v0.5.2), click "Create new tag on publish"
  • Click "Generate release notes" (this should give the release the same title as the tag (e.g. "v0.5.2")
  • Edit the "What's New" section into "Features" and "Fixes", simplify and combine PR bullet points
  • Publish release
• Wait for CI to run - this should trigger the "package" workflow in GitHub Actions and push to PyPI