Add overview of key features of Modelica to front page

[t-sommer]

with short examples, similar to https://www.python.org/.

Key Features:

Equation Based

Define the equations and let the compiler do the work.

Unit Safety

Connect components with confidence.

Object Oriented

Create models with different levels of complexity.

Modelica Standard Library

Comprehensive standard library with building blocks and examples from all physical domains.

Graphical Modeling

Create and parameterize models in a graphical environment.

Multi Domain

Simulation of multiple physical domains in one environment, e.g. thermal, electrical, mechanical, and logical.

[dzimmer]

I agree that this a good example. The exact details will be always subject to discussion. I will generate content so that we can realize this.