Add minimal example

[DanielKuebi]

To check if all modules work as expected and to provide more assistance to external users a minimal viable test case is required. This should include:

• Example traffic model
• Example traffic counting data
• Example workflow for pre-processing and inventory calculation
• Example workflow for post-processing

Ideas for open source data that could be included: BAST traffic counting data, Open Transport Map

-> Discussion with HBEFA required on how to include HBEFA emission factors