Add setup for user and developer documentation

[oruebel]

This PR adds the basic setup for creating custom pages for the user and developer documentation. Currently this looks as follows.

CHANGES

• Basic Setup
  • Added setup for creating User Docs and Developer Docs sections
  • Added setup for creating testable code examples as part of the tests/examples folder. The code in the folder is being executed with the regular tests, but has additional markup to be able to include specific sections of the code in the docs. In this way the code snippets in the docs are being tests with the regular test suite.
  • Added .codespell_ignore file to ignore Doxygen commands when running codespell
• New Documentation Pages
  • Moved requirements and installation instructions from the README to a dedicated page in the docs
  • Moved LICENCE and COPYRIGHT pages from the README to the docs
  • Added brief developer docs about testing
  • Add docs for SWMR mode and chunking in HDF5
  • Add example for making dot figures inline as part of the HDF5IO docs
  • Add documentation about how to write Docs (including code examples)
• Source Code Changes
  • Added BaseIO::flush() and HDF5IO::flush()
  • Fixed format conversion warnings in HDF5 tests
  • Added missing docstrings for namespaces

TODO (possibly for future PR)

• Expand the testing docs to also include other tests (e.g., sanitize) that a user should run
• Add developer dosc about how to edit documentation
• Add Getting Started page for users
• Add tutorial on how to integrate AqNWB with a data acquisition system
• Add docs on how to implement an alternate storage backend

[oruebel]

@stephprince would you prefer we define the basic setup here first and then add actual content for the docs in a separate PR or would you like me to add content (e.g., to describe SWMR) in this PR, so that we one PR for documentation content?

[stephprince]

@oruebel I'm ok adding content all in this PR, so we don't have placeholders and since the folder structure may change as you make the content.

[oruebel]

@stephprince please take a look. The main setup, outline, and a few additional docs pages are there. Given that this PR is already getting pretty big, I think it may be useful to use separate PR's to add more content to the docs.

[stephprince]

All the documentation and the diagrams look great! Added my suggestions.

[oruebel]

@stephprince can you take another look. I believe I've addressed all your comments. I also added a new page to describe some of the details about how to add content to the documentation.

[stephprince]

A few small changes to the section about adding new documentation but otherwise looks good!

[oruebel]

A few small changes to the section about adding new documentation but otherwise looks good!

Thanks for the additional comments. I committed all your suggestions.