fix(windows): remove the need for admin

[lidel]

Seems symllink now triggers admin prompt.

Running NPM with admin is not wise, instead we fallback to copying when on Windows.

• [x] fix #68
  • confirmed this works on borrowed Windows 10 laptop:
  • [x] npm i --save kubo@0.29.0-rc2 produced EPERM error
  • [x] npm i --save ipfs/npm-kubo#pull/74/head installed just fine, and without prompting for Admin
• [x] update CI in this repo to run tests on macos and windows
• [x] test in https://github.com/ipfs/ipfs-desktop/pull/1856 with latest LTS

Closes #68