Improve docs

[sverhoeven]

• README.md
  • [ ] Add introduction from docs/introduction.rst to README.md as currently intro is a bit short.
  • [ ] Move client site to top of usage as most users will use client
  • [ ] Link TLDR code snippets to doc website for more info.
• [ ] Add code of conduct
• [ ] Add contributing docs
  • [ ] Move README.md#development-generating-the-grpc-code
  • [ ] How to run tests #80
  • [ ] How to make new release + publish to pypi
• docs/
  • [ ] Use sections of README on index page, for example see https://github.com/phenology/springtime/blob/main/docs/index.md
  • [ ] Add links from rst to apidocs for even more examples or move examples to rst files.
• docstrings
  • [ ] create_grpc_channel + get_unique_port in BmiClient
  • [ ] get_value_ref in BmiClientApptainer