Add section on tools on landing page

Two important tools around preCICE have reached a certain level of maturity such that we should advertise them more prominently. They might attract new user communities:
- Micro Manager
- FMI-preCICE Runner

We could add a dedicated section on such tools on the landing page, maybe between "adapters" and "what our community is saying". With short explanations on what users can do with these tools:
- "Perform many-to-one macro-micro simulations with the preCICE Micro Manager"
- "Couple FMUs to PDEs with the FMI-preCICE Runner"

Each tool could become a card with a visual (with a similar style as the features on the landing page), such that we could also extend this list in the future.

Links should go to dedicated pages under `docs/tooling` (WIP for both tools).

I am not sure whether to add more of our tools here (config visualizer, ASTE, ...). These are hard to understand without knowing preCICE already.