improvement: faster shouldForwardProp

[agriffis]

Summary

Checking propSet.has() takes about 1/20 the time as checking props.includes() for the 2500+ props in xstyled v2.

Even with a shorter list, say 100 props, it's still 1/2 the time, so this perf benefit carries over from v2 to v3.

Test plan

I didn't test the perf difference directly with xstyled, but simple node. All times in milliseconds.

2500 element test

> words = fs.readFileSync('/usr/share/dict/words', {encoding: 'utf8'}).trim().split(/\s+/).slice(0, 2500)
> words.length
2500

> performance.mark('A'); for (let i = 0; i < 1000; i++) {words.includes('z')}; performance.measure('', 'A')
2.639519

> wordSet = new Set(words)
> performance.mark('B'); for (let i = 0; i < 1000; i++) {wordSet.has('z')}; performance.measure('', 'B')
0.106556

100 element test

> words = words.slice(0, 100)
> words.length
100

> performance.mark('A'); for (let i = 0; i < 1000; i++) {words.includes('z')}; performance.measure('', 'A')
0.194431

> wordSet = new Set(words)
> performance.mark('B'); for (let i = 0; i < 1000; i++) {wordSet.has('z')}; performance.measure('', 'B')
0.088844

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[gregberge]

@agriffis you can target next too for this one

[agriffis]

Ah, it looks like I could fast-forward merge with the "rebase and merge" option in GitHub (even though it was already rebased, so there was nothing to do)