Merge pull request #187 from fukayatsu/fix-rgba-leading-dot-alpha #215

Job	Run time
Test ruby version matrix (3.3)	53s
Test ruby version matrix (jruby)	1m 19s
Test ruby version matrix (3.4)	51s
Run rubocop	33s
Test ruby version matrix (4.0)	46s
	4m 22s

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