Add detail to git install instructions in README #250

Job	Run time
Build example plugins with CMake and JUCE 6.0.7 on ubuntu-latest	2m 37s
Build example plugins with CMake and JUCE 6.1.5 on ubuntu-latest	2m 55s
Build example plugins with CMake and JUCE 6.1.6 on ubuntu-latest	2m 46s
Build example plugins with CMake and JUCE 7.0.0 on ubuntu-latest	2m 53s
Build example plugins with CMake and JUCE 7.0.6 on ubuntu-latest	3m 5s
Build example plugins with CMake and JUCE 6.0.7 on windows-2019	2m 54s
Build example plugins with CMake and JUCE 6.1.5 on windows-2019	3m 30s
Build example plugins with CMake and JUCE 6.1.6 on windows-2019	2m 46s
Build example plugins with CMake and JUCE 7.0.0 on windows-2019	3m 45s
Build example plugins with CMake and JUCE 7.0.6 on windows-2019	2m 55s
Build example plugins with CMake and JUCE 6.0.7 on macOS-latest	2m 7s
Build example plugins with CMake and JUCE 6.1.5 on macOS-latest	2m 4s
Build example plugins with CMake and JUCE 6.1.6 on macOS-latest	2m 6s
Build example plugins with CMake and JUCE 7.0.0 on macOS-latest	2m 10s
Build example plugins with CMake and JUCE 7.0.6 on macOS-latest	2m 23s
	40m 56s

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