Update README.md (#109506)

Author: godofredoc

README.md

@@ -11,6 +11,7 @@
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 [![Twitter handle][]][Twitter badge]
 [![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/5631/badge)](https://bestpractices.coreinfrastructure.org/projects/5631)
+[![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/flutter/flutter/badge)](https://api.securityscorecards.dev/projects/github.com/flutter/flutter)
 
 Flutter is Google's SDK for crafting beautiful, fast user experiences for
 mobile, web, and desktop from a single codebase. Flutter works with existing