Use upstream Blob directly in typings

[LinusU]

Alternative approach to #37

I think that the reason that these were included in the first place was because they weren't present in upstream TypeScript at the time. This have been fixed now with: microsoft/TypeScript#36164

The drawback of this is that we are removing [Symbol.toStringTag] and toString. But if we think that it's correct to have them on the Blob I think it would be better to submit patches upstream to add that instead, since the idea behind this package is to bring Blob cross platform.

Since we haven't yet published a version with typings this would not be a breaking change!

Closes: #37

[codecov]

Codecov Report

Merging #38 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #38   +/-   ##
=======================================
  Coverage   86.95%   86.95%           
=======================================
  Files           1        1           
  Lines          69       69           
  Branches       13       13           
=======================================
  Hits           60       60           
  Misses          9        9           

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[LinusU]

Tests are failing because xo doesn't realise that Blob is defined (funny it worked with extends 😄)

edit: fixed, amended commit, and pushed

[LinusU]

Thanks for the quick reviews ❤️