docs: add glossary and FAQ links to 404 page

[JANANI-RS06]

What does this PR do?

Adds Glossary and FAQ links to the 404 page, with short descriptions matching the existing page tone.

Linked issue

Closes #39

How did you test this?

• Ran python -m http.server 8000 locally.
• Opened http://localhost:8000/404.html in the browser.
• Verified that the Glossary link appears and opens glossary.html.
• Verified that the FAQ link appears and opens faq.html.
• Ran git diff --check successfully with no errors.

Screenshots / terminal output

The 404 page was tested locally and both new links were verified to work.

Checklist

• I claimed this issue and it is assigned to me
• My branch is named feat/..., fix/..., or docs/...
• I only changed files related to this one issue
• I ran the project locally and it works
• CI checks below are green (or I have said why they are not)
• I am not adding my name to the README or reformatting files just to raise a PR

[github-actions]

Congratulations on your first pull request to this repository.

Here is what happens next:

1. The checks below need to go green. If one is red, click Details to see why — that is normal, and fixing it is part of the work
2. A maintainer reviews within 48 hours and may leave line comments
3. Once it is approved, a maintainer merges it

Two things that get PRs closed, so please double-check:

• No Closes #<issue> in the description
• The issue was never assigned to you

Nice work getting this far. Most people never open their first PR.