Add some units documentation

[The9Cat]

Overview

• Description of overall strategy
• Define the data structures in HDF5
• Describe the UI in pyEXP and C++
• Give an example of the HDF5 schema
• Provide an example of adding units using h5py

Tests

• Checked formatting of Sphinx-rendered HTML

To be done

• Possibly some additional detail
• Possible add some explicit usage cases and examples

[Copilot]

Pull Request Overview

This PR adds comprehensive documentation for physical units in EXP and pyEXP, explaining the unit system, schema, and HDF5 storage format.

• Introduces a new documentation page explaining the unit system used in EXP and pyEXP
• Documents the unit schema, interface methods, and HDF5 storage specification
• Includes code examples for setting units in both Python and C++

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 7 comments.

File	Description
topics/units.rst	New documentation file explaining units in EXP and pyEXP, including schema, interface, and HDF5 specification
index.rst	Added reference to the new units documentation page

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull Request Overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.