Web app design workshops

Added

• workshop for plotly dash (#22, #25)
• workshop for flask (#23, #25)
• workshop for fastapi (#24)

Add new workshop

Added

• workshop on test driven development (#15)

Exercises solutions

Merge pull request #12 from rl-institut/release/v0.1.1

Release/v0.1.1

First release of the workshop

This release contains two one-day workshops:

• one for python basics and essentials (with exercises).
• one for oemof (with exercises).