chore: Update codespell.yml to skip excalidraw files

[askulkarni2]

What does this PR do?

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Motivation

The current codespell workflow checks fail on .excalidraw file which should be checked for spellings. This PR skips those files from being spellchecked.

More

• Yes, I have tested the PR using my local account setup (Provide any test evidence report under Additional Notes)
• Mandatory for new blueprints. Yes, I have added a example to support my blueprint PR
• Mandatory for new blueprints. Yes, I have updated the website/docs or website/blog section for this feature
• Yes, I ran pre-commit run -a with this PR. Link for installing pre-commit locally

For Moderators

• E2E Test successfully complete before merge?

Additional Notes