new_audit(document compatibility check for quirks mode): added

[k99sharma]

Summary

Type of PR
Additional condition checking

Need for change
Lighthouse overlooked compatibility check for quirks mode in case of incorrect doctype. I added an additional check for compatibility with an additional explanation message explanationWrongDoctype in UIStrings.

Documentation
I looked at this: compatMode MDN doc for more information about compatibility check.

Related Issues/PRs
PR to fix the issue no: #10030

And sorry for the extra changes my IDE automatically converted single quotes into double quotes

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[k99sharma]

@googlebot I signed it!