Get rid of raf library

[darkowic]

I'm submitting a ...

• bug report
• feature request
• support request

The requestAnimationFrame is now widely supported by browsers -https://caniuse.com/#search=requestanimationframe

The library is using polyfill for it - https://www.npmjs.com/package/raf . Removing the polyfill we could save ~30% of build size https://bundlephobia.com/result?p=react-sticky@6.0.3

[vcarl]

This is a good idea! You're right, I feel fine not supporting older than IE10. I'll see about making this change soon.

[SleepWalker]

moreover raf is required for recent React versions. So it should be actually already polyfilled by lib consumers.