Allow workspaceRoot variable in pathToFlow

[rattrayalex]

flow.useNPMPackagedFlow wasn't adequate for my use-cases (node_modules not at root, a copy for flow-bin outside of node-modules, etc).

I was resorting to this hack: "postinstall": "cp .vscode/settings.example.json .vscode/settings.json && sed -i '' \"s ROOT_REPLACE_ME $(pwd) \" .vscode/settings.json"

Ideally this would be solved by vscode; there is an open issue: microsoft/vscode#2809 however it seems harmless to add this.

I tested locally with:

• setting defined correctly ("flow.pathToFlow": "${workspaceRoot}/my-flow")
• setting defined incorrectly ("flow.pathToFlow": "${workspaceRoot}/my-nonexistent-flow")
• setting undefined (checking that .config('pathToFlow').replace does not throw)

[orta]

This is 👍 from me, any chance you can add some docs in the README for this first?

[rattrayalex]

Hmm, I won't be able to get to that shortly... I can try to get to it within a few days.

[rattrayalex]

(Feel free to merge without if you're comfortable with that, I'm happy to submit a follow-on PR if that's okay by you)

[orta]

👍 that's fine by me, yeah