Add ability to define annotations for web/worker Service accounts

[Caprowni]

Existing Issue

Fixes #173

Changes proposed in this pull request

• Adds annotations variables for both worker and web since they might have different use cases for annotations, these are defined inside the values.yaml and will be rendered(if there are any) into chart at runtime.
• Adds the annotation include statements into the web and worker service account template files.

Contributor Checklist

• [x] Variables are documented in the README.md
• [x] Which branch are you merging into?
  • master is for changes related to the current release of the concourse/concourse:latest image and should be good to publish immediately

Merging to master should be okay (?) happy to move to dev if need be, as I mentioned i've already worked around this by creating my own service accounts but would be nice to have this natively supported.

Reviewer Checklist

This section is intended for the core maintainers only, to track review progress. Please do not fill out this section.

• [ ] Code reviewed
• [ ] Topgun tests run
• [ ] Back-port if needed
• [ ] Is the correct branch targeted? (master or dev)

[Caprowni]

@YoussB Hey! Thanks for reviewing my PR, I fixed the indentation you mentioned, i'm not sure about the values.yaml comment though as i've already added the definitions into the values.yaml at the root of the repo.

Is there something i've missed?