Make blackbox easier to include in a docker dev container

[Ed Burnette]

I'd like to use blackbox from a docker container (namely a dev container in VSCode) but all the current ways to install it require extra steps. I can think of 3 ways to do this:

1. Create a dev container feature, as described in https://code.visualstudio.com/docs/remote/containers#_dev-container-features-preview .
2. Allow installation with an npm command such as: npm install -g @stackexchange/blackbox
3. Provide an installation script that can be used like: curl https://raw.githubusercontent.com/StackExchange/blackbox/master/install.sh | bash