feat: allow selenium server with internal webserver

[daFish]

Implements #590 by @dkarlovi.

This change allows the usage of an external selenium instance (e.g. via docker compose) to test against the internal webserver.

Todos:

• [ ] Tests
• [ ] Documentation

[dkarlovi]

permission of @dkarlovi

What "permission", thank you so much for working on this! \o/ :smile:

[daFish]

Coding Standards fails seem unrelated.

@dkarlovi Ok, let's rephrase it then. 😄

[dkarlovi]

@daFish this looks completed to me, why did you leave is as a draft?

[daFish]

@daFish this looks completed to me, why did you leave is as a draft?

I made a small info in the README about it. I will remove the draft status and this is good to go.