[Refactor] use a global variable to get the original BigInt instead of a global property

[triptate]

not all bundlers polyfill the node global variable. this change makes the library work universally in node or the browser, whether global is polyfilled or not.

a discussion of the issue for a similar library is here: inspect-js/has-symbols#11

[codecov]

Codecov Report

Merging #11 (a7ccfac) into main (62d31e7) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main       #11   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines            6         6           
  Branches         4         5    +1     
=========================================
  Hits             6         6           

Impacted Files	Coverage Δ
index.js	100.00% <100.00%> (ø)

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[ljharb]

All bundlers that aren't broken do - a node module bundler's job is to provide node globals and shims for node builtins whenever possible.

[ljharb]

Same comment as in inspect-js/has-symbols#11 (comment): stop using a bundler that's broken. However, this is still equally correct, so I suppose it's fine.

[triptate]

i don't really have a horse in this fight, but here is the perspective from the Vite team: vitejs/vite#5912 (comment)

[ljharb]

I realize that, and I'd strongly encourage people to avoid a bundler with that attitude like the plague. A node module bundler that does not polyfill node globals is not a node module bundler.