Add codespell integration for spell checking

[aroramrinaal]

This pull request adds codespell integration to the project, enabling automated spell checking for common misspellings in the source code. By running codespell on each pull request targeting the gh-pages branch.

closes #4555

[shiftbot]

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[shiftkey]

Can we go even simpler and just use the Action for codespell?

[shiftkey]

Looks like at least assets/upforgrabs.ai should be ignored by codespell, as that's not a text file

[RayBB]

@aroramrinaal can you update the PR with these suggestions?

[shiftkey]

Closing in favour of https://github.com/up-for-grabs/up-for-grabs.net/pull/4703 which gets this working on CI and addresses regressions