Document disabling response templating per stub

[leeturner]

This PR adds a few small updates to the community docs based on some questions that were asked and answered in the community slack recently:

• Update the docker compose example where we map the directories to include the extensions directory
• Add an example of disabling response templating on a per stub basis

Submitter checklist

• [x] The PR request is well described and justified, including the body and the references
• [x] The PR title represents the desired changelog entry
• [x] If the change against WireMock 2 functionality (incompatible with WireMock 3), it is submitted against the 2.x branch
• [x] The repository's code style is followed (see the contributing guide)

Details: Contributor Guide