Fixes for seat-adjuster example

[BjoernAtBosch]

Describe your changes

• Make hint that seat-adjuster example can only be run in template repository more prominent in main README
• Explain how to import and run seat-adjuster example in template repo in that example's README
• Remove usage of bracket operators for seat row and pos as quick fix for [Bug] Index-based access to VSS instances, e.g. Vehicle.Cabin.Seat.Row(1).Pos(2). ..., not offered by generated model vehicle-app-python-template#159
• Quickfix of Dockerfile: Add missing inclusion of the generated vehicle model

Issue ticket number and link

• Fix for [Bug]: SeatAdjuster App: ModuleNotFoundError: No module named 'vehicle' #79 and Readme for Seat-Adjuster needs update #82
• Quick fix for [Bug]: Seat Adjuster Dockerfile is not buildable "stand-alone" #84: With that the Dockerfile is not buildable "stand-alone", but can be build from vehicle-app-python-template (and instances). Explanation added in examples README.

Checklist - Manual tasks

• Examples are executing successfully
• Created/updated unit tests. Code Coverage percentage on new code shall be >= 80%.
• Created/updated integration tests.
• Devcontainer can be opened successfully
• Devcontainer can be opened successfully behind a corporate proxy
• Devcontainer can be re-built successfully
• Extended the documentation (e.g. README.md, CONTRIBUTING.md, Velocitas)

[doosuu]

LGTM

[kse3hi]

LGTM