Add note about Unicode::SequenceName #18

Job	Run time
Ruby 3.3 (windows-latest)	2m 58s
Ruby 3.2 (windows-latest)	2m 9s
Ruby 3.3 (ubuntu-latest)	10s
Ruby 3.1 (windows-latest)	2m 9s
Ruby 3.3 (macos-latest)	9s
Ruby 3.0 (windows-latest)	2m 10s
Ruby 3.2 (ubuntu-latest)	9s
Ruby jruby (windows-latest)	2m 58s
Ruby 3.2 (macos-latest)	10s
Ruby 3.1 (ubuntu-latest)	6s
Ruby 3.1 (macos-latest)	10s
Ruby 3.0 (ubuntu-latest)	9s
Ruby 3.0 (macos-latest)	11s
Ruby jruby (ubuntu-latest)	28s
Ruby jruby (macos-latest)	20s
Ruby truffleruby (ubuntu-latest)	16s
Ruby truffleruby (macos-latest)	17s
	14m 59s

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