Add a link back to the experiment from the policy server docs

[slinlee]

No description provided.

[maxpumperla]

@slinlee the URL of an experiment is constructed as follows (as you know, just documenting this here):

https://app.pathmind.com/project/<id>/model/<id>

if we optionally write, say:

  model_id: 1234
  project_id: 5678

into the schema.yaml from the web app, we can pick that up in the docs, by modifying the HTML. I've done this experimentally, looks as follows:

I think that's the best way to go forward, so I'll finish that up quickly.

[slinlee]

@maxpumperla if we are deploying policy servers from prod, staging, and test, do you think it's easier if we just pass the full URL as the param in the schema.yaml file?

[maxpumperla]

@slinlee yeah, didn't think of that, but makes a lot of sense. I'll put that in there.

btw, as you can see in the PR, we can modify the CSS as we like, in case there are things we want to tweak. I just put the bare minimum there that didn't look too awful.