Added OpenSSF Scorecard Badge for Security Insights

[kiselik]

trafficstars

more details are listed in https://github.com/google/googletest/issues/4808

[google-cla[bot]]

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[kiselik]

@derekmauro I amn't sure who exactly is responsible for reviewing external PRs, but I've found your name in the "release" section

would it be possible take a look on this?