update URL

[KaiWaldrant]

Describe your changes

change the png url and website url for viash cheat sheet

Checklist before requesting a review

• [x] I have performed a self-review of my code

• Check the correct box. Does this PR contain:

  • [ ] Breaking changes
  • [ ] New functionality
  • [ ] Major changes
  • [ ] Minor changes
  • [x] Bug fixes

• [x] Proposed changes are described in the CHANGELOG.md

• [x] CI Preview succeeds and looks good!

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