Feature: Allows the use of Docker Volume Mount for /zap/wrk/

[lloyd-j0nes]

Hi ZAProxy team,

First off, amazing work on this! It's really slick and I'm loving how simple it is to use.

We currently use GitHub Enterprise on-premise, with runners that are containerized. This presents a problem when trying to do bind mounts for the /zap/wrk directory, as the container can't bind mount its own filesystem to another container. Would it be feasible to allow overriding the -v argument in the docker command that's currently set to ${workspace}/process.env.GITHUB_WORKSPACE?

From:

let workspace = process.env.GITHUB_WORKSPACE; 
let command = ('docker run -v ${workspace}:/zap/wrk/:rw --network="host"  +

To:

<Check for storagesrc variable, if not set, default to process.env.GITHUB_WORKSPACE>
let command = ('docker run -v ${storagesrc}:/zap/wrk/:rw --network="host"  +

For example, if we could pass the name of a docker volume or our own path, that would resolve this issue. Other may run into this if they are using their own containerized/on-prem environments, so it may be useful in other cases as well.