feat: Safe assignment polyfill V2, introducing Function#result() method

[otaxhu]

This pull request solves some problems discussed on many issues:

credits to @rockedpanda comment in #45 issue.

• It doesn't introduce special syntax nor punctuation tokens that is very hard to parse or understand by humans.
  This problem was mentioned in this issues: Unexpected parsing inconsistency #38
• It doesn't bring up order-matters problems.
  This problem was mentioned in this issues: Prior art to safe assignment operator proposal #41
  It basically talks about the order of the following expressions:

  // most likely this is the only correct way, since we wrapping await
  // with try expression;
  const [parseError, json] = try await response.json();
  
  // anyways most likely there will be such cases, and this will be syntax error
  // on Babel, ESLint and Typescript
  // or runtime error when json has promise, instead of result
  const [parseError, json] = await try response.json();

Some examples usage of this new polyfill:

// Function.result() returns a promise if the underlying function returns a promise.
const [error, response] = await fetch.result("https://example.org");
// You can't forget the order, any function has the method result (even async functions)

const [error, obj] = JSON.parse.result("bad");

[otaxhu]

I didn't test it before opening the pull request, it has a lot of problems with Window object functions like fetch(), the this context changes when calling fetch.result() method, making the call to throw with an error TypeError: 'fetch' called on an object that does not implement interface Window.