docs: update address of china mirror

[hyj1991]

Hi, thanks for the excellent work of nvm-windows.

For some regulatory reasons, we will offline npm.taobao.org at 2022.05.21, and the new domain name is npmmirror.com.

Actually, the service that npm.taobao.org provided before has not changed:

nslookup npmmirror.com
Server:		30.30.30.30
Address:	30.30.30.30#53

Non-authoritative answer:
Name:	npmmirror.com
Address: 47.96.233.62

-----------

nslookup npm.taobao.org
Server:		30.30.30.30
Address:	30.30.30.30#53

Non-authoritative answer:
Name:	npm.taobao.org
Address: 114.55.80.225

We just re-registered a domain name and new SLB (Server Load Balancing) due to regulatory reasons.

Reference: https://zhuanlan.zhihu.com/p/430580607

[coreybutler]

Thank you for this!

[hetz]

npm Mirror address error, #759