Add is.propertyKey

[PopGoesTheWza]

Fixes #136

[PopGoesTheWza]

@sindresorhus older version of Typescript may not include Symbol in the PropertyKey definition. Would that be an issue?

[sindresorhus]

You need to add it to the readme.

[gioragutt]

The test needs a fix, otherwise looks good. Never knew PropertyKey was a built-in type, always used keyof any instead. Thanks for the info :)

[PopGoesTheWza]

Never knew PropertyKey was a built-in type, always used keyof any instead.

Ouch! I used string | number before venturing in the Typescript standard libraries (which is full of good information). Support for symbol keys was added recently to Typescript.

[gioragutt]

The comment about the comment wasn't fixed. I believe this would be the last change

[gioragutt]

@PopGoesTheWza thanks for your contribution bro 🤘🏻

[PopGoesTheWza]

thanks for your contribution bro

On a totally irrelevant and lighthearted matter, I viscerally hate the term "bro". I can do with "dude" or "mate" though... ;)

[gioragutt]

@PopGoesTheWza I swear I thought about it ASA I posted the comment 😅 Thanks for pointing it out 🙏🏻