Docs improvement (#1278) #1994

Job	Run time
Build Echidna on ubuntu-20.04	5m 47s
Build Echidna on macos-13	36m 49s
Build Echidna on windows-latest	26m 50s
Test with solc 0.4.25 on ubuntu-latest	4m 50s
Test with solc 0.5.7 on ubuntu-latest	3m 57s
Test with solc 0.6.12 on ubuntu-latest	3m 25s
Test with solc 0.7.5 on ubuntu-latest	3m 44s
Test with solc 0.4.25 on windows-latest	4m 11s
Test with solc 0.5.7 on windows-latest	3m 32s
Test with solc 0.6.12 on windows-latest	3m 41s
Test with solc 0.7.5 on windows-latest	4m 12s
	1h 40m 58s

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