Fix typos in README.md file

[aalty]

Line 177: Compatiblity → Compatibility
Line 181: does't → doesn't
Line 274: forgotton → forgotten

[googlebot]

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[aalty]

I signed it!

[googlebot]

CLAs look good, thanks!

[erickoledadevrel]

Thanks so much! I should know by now to spell check my README files :-P

[aalty]

@erickoledadevrel Much more thanks to this great library :D