Add automated check for docs build

[melissawm]

Description

This PR adds a simple check to the CI workflows that verifies the documentation build. This will prevent accidental breakage of the docs.

It also includes a new item in the PR template checklist to make sure new documentation pages are correctly added to the Table of Contents.

Tests

I tested the workflow locally using act.

Checklist

Before submitting this PR, please make sure (put X in square brackets):

• I have performed a self-review of my code.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have run end-to-end tests tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed.