feat(utils): Add isNaN function

[lobsterkatie]

This adds a function, isNaN, to our is module. While it's true that there is a built-in function of the same name, it assumes it's being passed a number (which messes up types), whereas the function introduced here makes no such assumptions.

(This change was extracted from an upcoming PR, to reduce noise there.)

[github-actions]

size-limit report

Path	Base Size (1379591)	Current Size	Change
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.49 KB	19.49 KB	-0.02% 🔽
@sentry/browser - ES5 CDN Bundle (minified)	62.17 KB	62.17 KB	0%
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.12 KB	18.11 KB	-0.02% 🔽
@sentry/browser - ES6 CDN Bundle (minified)	55.5 KB	55.5 KB	0%
@sentry/browser - Webpack (gzipped + minified)	22.6 KB	22.6 KB	0%
@sentry/browser - Webpack (minified)	79.21 KB	79.21 KB	0%
@sentry/react - Webpack (gzipped + minified)	22.63 KB	22.63 KB	0%
@sentry/nextjs Client - Webpack (gzipped + minified)	47.6 KB	47.6 KB	0%
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	25.37 KB	25.36 KB	-0.01% 🔽
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	23.72 KB	23.72 KB	-0.01% 🔽

[Lms24]

Nice TIL about the inequality of NaN to NaN (which totally makes sense after reading up on it). Looks good to me + nice test. My only question is, do we currently need this function somewhere or is it there to be used eventually? I get why it makes sense use this function over the built-in isNaN, just asking b/c I don't see it being used at this point.

[lobsterkatie]

My only question is, do we currently need this function somewhere or is it there to be used eventually?

Yup, sorry - have added a note to the PR description.