Readme: updated documentation badge #3343

Job	Run time
Linux -> Pre-checks	13s
Linux -> GCC-x64, Debug	11m 56s
Linux -> GCC-x64, Release	10m 14s
Linux -> Clang-x64, Debug	12m 35s
Linux -> Clang-x64, Release	12m 17s
Linux -> Clang-NO_GLSLANG-x64, Debug	7m 38s
Linux -> Clang-NO_GLSLANG-NO_HLSL-x64, Release	5m 58s
	1h 0m 51s

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