Speed up the npm installation process

[xqin]

Since the authors in jail, so he has no need to find a job.

So let's remove postinstall, speed up the npm installation process for everybody.

related issues:

#767

#548

#797

#757

#781

#729

#708

https://github.com/zloirock/core-js/issues?q=is%3Aissue+install

[JakeChampion]

If you want to silence the output then you can set any one of these environment variables before running npm install:

ADBLOCK
CI
DISABLE_OPENCOLLECTIVE
SILENT
OPEN_SOURCE_CONTRIBUTOR

[xqin]

If you want to silence the output then you can set any one of these environment variables before running npm install:

ADBLOCK
CI
DISABLE_OPENCOLLECTIVE
SILENT
OPEN_SOURCE_CONTRIBUTOR

I don't want to output silently, I want to remove postinstall to speed up the installation.

[JakeChampion]

The author of this project does not want to remove it