Change globalObject to globalThis

[kkocdko]

I want to run docs.js in some embed js engine which have not this defined in global namespace (and es module also haven't).

Compatibility: not a problem, globalThis was added in ES6, and this project's tsconfig.json also uses ES6 target.

https://github.com/dolanmiu/docx/blob/master/tsconfig.json#L3

[codecov-commenter]

Codecov Report

Base: 99.70% // Head: 99.70% // No change to project coverage 👍

Coverage data is based on head (482ea1b) compared to base (7e5e2ba).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1725   +/-   ##
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  Coverage   99.70%   99.70%           
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  Files         319      319           
  Lines        3704     3704           
  Branches      405      405           
=======================================
  Hits         3693     3693           
  Misses         11       11           

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[dolanmiu]

I am not sure about this, this will break docx on the web:

Docs from webpack:

https://webpack.js.org/configuration/output/#outputglobalobject

To make UMD build available on both browsers and Node.js, set output.globalObject option to 'this'

[kkocdko]

Webpack doc: To make UMD build available on both browsers and Node.js, set output.globalObject option to 'this'

I think this description is just for legacy. I have tried on Chrome, Firefox, Deno, Node, QuickJS and their ESModule enviroument. There's no reason that globalThis will break on web environment. And,

MDN: this will be undefined in Modules

So the most important problem is compatibility. Chrome >= 71, Firefox >= 65, no IE supports. But I'm not sure what target docx.js supports before? If you prefer to keep compatibility, fell free to close this PR, I'll just patch it in my enviroument.

[dolanmiu]

Ok, sounds good, I will double check tomorrow, if its good, I will merge

[dolanmiu]

Looks good to me, merging