Note about usage on README #6

Job	Run time
Clang Build (5.1.5)	26s
Build C++ (5.1.5, true)	24s
MSYS2 Build (mingw64, x86_64, 5.4, lua, lua)	48s
Clang Build (5.2.4)	30s
Build C++ (5.1.5, false)	18s
Build (5.1, windows-latest)	9s
MSYS2 Build (mingw64, x86_64, 5.3, lua53, lua5.3)	55s
Clang Build (5.3.6)	53s
Build C++ (5.2.4, true)	34s
Build (5.1, ubuntu-latest)	12s
MSYS2 Build (mingw64, x86_64, 5.1, lua51, lua5.1)	52s
Clang Build (5.4.7)	22s
Build C++ (5.2.4, false)	29s
Build (5.1, macos-latest)	16s
MSYS2 Build (mingw64, x86_64, 5.1, luajit, luajit)	46s
Build C++ (5.3.6, true)	29s
Build (5.2, windows-latest)	1s
MSYS2 Build (ucrt64, ucrt-x86_64, 5.4, lua, lua)	55s
Build C++ (5.3.6, false)	33s
Build (5.2, ubuntu-latest)	13s
MSYS2 Build (ucrt64, ucrt-x86_64, 5.3, lua53, lua5.3)	55s
Build C++ (5.4.7, true)	24s
MSYS2 Build (ucrt64, ucrt-x86_64, 5.1, lua51, lua5.1)	57s
Build C++ (5.4.7, false)	25s
MSYS2 Build (ucrt64, ucrt-x86_64, 5.1, luajit, luajit)	1m 0s
Build (5.2, macos-latest)	16s
MSYS2 Build (clang64, clang-x86_64, 5.4, lua, lua)	1m 13s
Build (5.3, windows-latest)	1s
MSYS2 Build (clang64, clang-x86_64, 5.3, lua53, lua5.3)	1m 39s
Build (5.3, ubuntu-latest)	1s
MSYS2 Build (clang64, clang-x86_64, 5.1, lua51, lua5.1)	50s
Build (5.3, macos-latest)	13s
MSYS2 Build (clang64, clang-x86_64, 5.1, luajit, luajit)	1m 9s
Build (5.4, windows-latest)	1s
Build (5.4, ubuntu-latest)	1s
Build (5.4, macos-latest)	1s
Build (luajit, windows-latest)	1s
Build (luajit, ubuntu-latest)	1s
Upload rockspec	0s
	19m 13s

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