Add codespell to check for typos

[LukasWallrich]

Description

This adds a spell check to get control of the (not infrequent) typos.

Type of Change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Not yet - waiting for the action to run here, then I will tick the box.

• Successful GH action run

Checklist for Content Editors and Non-Developers

N/A

Checklist for Developers:

• I have attempted to stay aligned to related code in this repository rather than reinventing the wheel.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.

[github-actions]

👍 All image files/references (if any) are in webp format, in line with our policy.

[LukasWallrich]

Clearly does no work across .md files in content - see #283

[github-actions]

This pull request has been inactive for more than 90 days. If there is no further activity, it will be automatically closed in seven days time. You can reopen the pull request if it is still relevant.

[github-actions]

This pull request has been automatically closed due it being stale for more than 7 days. Please feel free to reopen if you still want to submit this pull request.

[github-actions]

This pull request has been inactive for more than 90 days. If there is no further activity, it will be automatically closed in seven days time. You can reopen the pull request if it is still relevant.

[flavioazevedo]

So should we just delete this because you @LukasWallrich said that it doesn't work?

[richarddushime]

still a draft , may be we can leave it