[DOC] document every function of pytta.functions and build on Read the Docs - #70

Updates the Sphinx documentation in docs/.

1. The functions page listed some functions of pytta.functions by hand and missed others (print_devices, split, pytta_save, pytta_load). It now documents the whole module with automodule :members:, so it lists all 24 public functions, and new functions appear without editing the page.
2. pytta.iso3741 gets its own page, linked from the API index.
3. Two entries made the build report errors: the utilities page pointed to pytta.utils.filter_alpha, which does not exist (the function is filter_values), and conf.py referred to a _static folder that is not in the repository. Both are fixed.
4. The release shown in the documentation is read from pytta.__version__. It said 0.1.0.
5. .readthedocs.yaml lets Read the Docs build the documentation with Python 3.12, Sphinx and the PortAudio library, which sounddevice needs at import. The installation page states the requirements.

Built locally with Sphinx: no errors. 25 warnings remain, all about the reStructuredText formatting inside docstrings (mostly in RoomAnalysis). I left them for later, since fixing them touches modules that several open pull requests change.

This is independent of #69: Read the Docs installs PyTTa with pip install ., which works with setup.py and with pyproject.toml.

Co-Authored-By: Claude Fable 5.1 noreply@anthropic.com