Fix missing link to mime-types-data gem in README #76

Job	Run time
Ruby 2.6 - macos-latest	1m 24s
Ruby 2.7 - macos-latest	1m 1s
Ruby 3.0 - macos-latest	31s
Ruby 3.1 - macos-latest	31s
Ruby 3.2 - macos-latest	27s
Ruby 3.3 - macos-latest	56s
Ruby head - macos-latest	26s
Ruby jruby - macos-latest	1m 37s
Ruby jruby-head - macos-latest	1m 56s
Ruby truffleruby - macos-latest	1m 48s
Ruby truffleruby+graalvm - macos-latest	9m 51s
Ruby 2.6 - ubuntu-20.04	45s
Ruby 2.7 - ubuntu-20.04	53s
Ruby 3.0 - ubuntu-20.04	24s
Ruby 3.1 - ubuntu-20.04	22s
Ruby 3.2 - ubuntu-20.04	21s
Ruby 3.3 - ubuntu-20.04	28s
Ruby head - ubuntu-20.04	14s
Ruby jruby - ubuntu-20.04	1m 17s
Ruby jruby-head - ubuntu-20.04	1m 20s
Ruby truffleruby - ubuntu-20.04	52s
Ruby truffleruby+graalvm - ubuntu-20.04	3m 30s
Ruby mingw - windows-latest	1m 20s
Ruby mswin - windows-latest	1m 18s
Ruby jruby - windows-latest	2m 28s
Ruby head - ubuntu-22.04	14s
Ruby 3.1 - ubuntu-22.04	25s
Ruby 3.2 - ubuntu-22.04	18s
Ruby 3.3 - ubuntu-22.04	34s
Ruby truffleruby+graalvm-head - ubuntu-22.04	3m 42s
Ruby truffleruby-head - ubuntu-22.04	1m 2s
	42m 15s

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