Add list of security reviews #1758

Job	Run time
Build Echidna on ubuntu-20.04	3m 46s
Build Echidna on macos-latest	2m 5s
Build Echidna on windows-latest	8m 19s
Test with solc 0.4.25 on ubuntu-latest	3m 17s
Test with solc 0.5.7 on ubuntu-latest	3m 44s
Test with solc 0.6.12 on ubuntu-latest	3m 27s
Test with solc 0.7.5 on ubuntu-latest	4m 3s
Test with solc 0.4.25 on windows-latest	4m 48s
Test with solc 0.5.7 on windows-latest	5m 19s
Test with solc 0.6.12 on windows-latest	5m 44s
Test with solc 0.7.5 on windows-latest	6m 21s
	50m 53s

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