Add Sphinx documentation for ReadTheDocs hosting

[Copilot]

NeSST had no formal documentation beyond the README and an example notebook. This adds a full Sphinx docs site suitable for hosting on ReadTheDocs.

Structure

• docs/conf.py — Sphinx config: sphinx-rtd-theme, autodoc + napoleon (Google docstrings), intersphinx, myst-parser, nbsphinx
• docs/index.rst — Top-level TOC
• docs/installation.rst — PyPI and source install instructions
• docs/guide.rst — User guide with worked examples covering primary spectra, scattered spectra, transmission, fitting, nToF, and materials
• docs/api.rst — Auto-generated API reference for all 8 modules via autodoc
• docs/example_notebook.rst — Links to the existing nbviewer-hosted Jupyter guide
• docs/requirements.txt — Docs build dependencies

ReadTheDocs integration

• .readthedocs.yaml — v2 config; Ubuntu 22.04, Python 3.11, installs package + docs deps, points to docs/conf.py
• pyproject.toml — Adds docs extras group (pip install NeSST[docs])
• .gitignore — Excludes docs/_build/

To enable: import the repo on readthedocs.org — .readthedocs.yaml is auto-detected.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• docs.python.org
  • Triggering command: /home/REDACTED/.local/bin/sphinx-build sphinx-build -M html . _build (dns block)
• docs.scipy.org
  • Triggering command: /home/REDACTED/.local/bin/sphinx-build sphinx-build -M html . _build (dns block)
• numpy.org
  • Triggering command: /home/REDACTED/.local/bin/sphinx-build sphinx-build -M html . _build (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

Based on the example notebook, readme and docstrings, can you create documentation for this package to be hosted on a readthedocs?

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✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.