Installation issue, url is blocked by our proxy.

## Issue or Feature
We are working on upgrading a new version of galata (v4.2.2) and "canvas" is one of the dependencies. We have an issue here: ‘node-canvas' install script tries to download the package from "{https://github.com/Automattic/node-canvas/releases/..."}, which is a url blocked by our company’s proxy (we literally block all third party urls). Canvas is available on our artifact, don't know why the install script doesn't pull the package from artifact. We are thinking to pre-install canvas manually in our docker container. However, we tried a few ways:

- “npm install --build-from-source” (from source code)

and

- “npm install package from tar.gz” (from tar.gz file)

both failed and it shows again it tries to download the pkg from the url (which is blocked by our proxy).

Error message:
```

node-pre-gyp ERR! install request to https://github.com/Automattic/node-canvas/releases/download/v2.9.1/canvas-v2.9.1-node-v72-linux-glibc-x64.tar.gz failed, reason: connect ECONNREFUSED 140.82.112.3:443
node-pre-gyp WARN Pre-built binaries not installable for canvas@2.9.1 and node@12.13.0 (node-v72 ABI, glibc) (falling back to source compile with node-gyp)
node-pre-gyp WARN Hit error request to https://github.com/Automattic/node-canvas/releases/download/v2.9.1/canvas-v2.9.1-node-v72-linux-glibc-x64.tar.gz failed, reason: connect ECONNREFUSED 140.82.112.3:443
```

Is there a way to pre install canvas and avoid download from that git url?