feat: Add workspace root substitution for docker containers

[domsleee]

Suggested feature for #199

It is a proof of concept of a way of transforming the test file path, that could be used in a docker container

For example, instead of this:

node 'node_modules/.bin/jest' '/Users/user/git/vscode-jest-runner/examples.test.ts' -t 'Example'

With testPathSubstitution as /app/container (i.e. a replacement of the workspace root):

node 'node_modules/.bin/jest' '/app/container/examples.test.ts' -t 'Example'

With testPathSubstitution as ./ (i.e. relative to workspace root):

node 'node_modules/.bin/jest' './examples.test.ts' -t 'Example'

[firsttris]

Let me know when you want to merge this because it's still in draft

[firsttris]

you also have to permission to merge on your own.