Critical CSS: add support for SVG within CSS

[kraftbj]

Fixes HOG-25 #42321

Proposed changes:

• Adds support for SVG by allowing safe elements.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
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Jetpack product discussion

n/a

Does this pull request change what data or activity we track or use?

No.

Testing instructions:

• None yet, need to actually add the code to make it work. Just a failing test right now to kick things off.

[github-actions]

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[jp-launch-control]

Code Coverage Summary

Cannot generate coverage summary while tests are failing. 🤐

Please fix the tests, or re-run the Code coverage job if it was something being flaky.

Full summary · PHP report · JS report