Stephan Rave

Rendered documentation is [here](https://docs.pymor.org/howto-guides/). My suggestion would be to merge this with #2266 and rename the howtos to 'frequently asked questions'. So far we always decided against having FAQs, but...

As discussed, I have cherry-picked the TOC changes into https://github.com/pymor/pymor/pull/2266. We will add an FAQ section similar to the howto-guides in this PR for the 2024.2.

> As far as I can tell, the optimization tutorial uses the problem from the linear_optimization.py demo -- which we simply import in the trust_region.py demo. We now have `pymor.models.examples`...

@peoe, @TiKeil, how should we proceed with this PR? I think this need to come to a conclusion. If need be, I can try to do it, but I'm not...

> Is there something to decide upon or is it "just" working on finalizing the PR ? I think it's just finalizing the tutorial.

@TiKeil, hard freeze for the next release is in one week. Do you think you find time to take a look at this until then?

> I'm afraid I will not be able to work on this before the freeze. But I will look at it asap. Ok, I'll remove the release milestone for now....

@TiKeil, did you have a chance to look at this PR? Soft freeze for the next release would be May 31 ..

@HenKlei, maybe you might want to take over. Should not be too much work to finalize this, I hope.

Precommit is still complaining, @HenKlei.