docs: Create glossary for units

[uwcdc]

Description:

We need to create a glossary for units to provide a reference for common units used throughout our project documentation. This glossary will help maintain consistency and clarity in our technical documentation.

Tasks:

• Create a new file named glossary.rst under the docs/ directory
• Populate glossary.rst with definitions of common units used in our project
• Update the _toc.yml file to include the glossary.rst file so that it appears in the table of contents of our JupyterBook instance

Acceptance Criteria:

The glossary.rst file should contain clear and concise definitions for each unit
The glossary.rst file should be formatted according to our documentation standards
The _toc.yml file should be updated to include the glossary.rst file
The glossary should be accessible and visible in the table of contents of our JupyterBook instance