Add an OpenSSF badge to README.md #15975

Job	Run time
test-bench	25s
lint	2m 20s
test-race	2m 16s
compatibility-test (1.23.0, ubuntu-latest, 386)	23s
test-concurrent-safe	4m 4s
compatibility-test (1.23.0, ubuntu-latest, amd64)	1m 19s
test-coverage	38s
compatibility-test (1.23.0, otel-linux-arm64, arm64)	31s
compatibility-test (1.23.0, macos-13, amd64)	1m 19s
compatibility-test (1.23.0, macos-latest, arm64)	38s
compatibility-test (1.23.0, windows-latest, 386)	3m 38s
compatibility-test (1.23.0, windows-latest, amd64)	2m 13s
compatibility-test (~1.22.5, ubuntu-latest, 386)	20s
compatibility-test (~1.22.5, ubuntu-latest, amd64)	1m 17s
compatibility-test (~1.22.5, otel-linux-arm64, arm64)	18s
compatibility-test (~1.22.5, macos-13, amd64)	52s
compatibility-test (~1.22.5, macos-latest, arm64)	37s
compatibility-test (~1.22.5, windows-latest, 386)	2m 58s
compatibility-test (~1.22.5, windows-latest, amd64)	2m 1s
codecov	4s
test-compatibility	1s
	28m 12s

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