Improving description for Hydra in Baselines

[pedropgusmao]

Reference Issues/PRs

NA

What does this implement/fix? Explain your changes.

Improves documentation on how to use Hydra

Any other comments?

[danieljanes]

One idea: should we perhaps move the new section after the TL;DR to avoid intimidating new contributors? The TL;DR is there to give a brief overview, the planning section is a more in-depth piece of content. Wdyt?

[pedropgusmao]

I see that the TL;DR was removed in this PR (?) https://github.com/adap/flower/blob/b9d5b4776a6fa202c8a85a2925f46d1f7999a66f/doc/source/contributing-baselines.rst

[pedropgusmao]

Tbh I'm reluctant to even have a TL;DR... I see this as a guide to creating baselines using hydra, so they kind of need to go through the document.

[tanertopal]

Closing in favor of new content which will be part of the SoR tutorials.

[jafermarq]

We have re-structured the baselines and some of these ideas have been incorporated. Hydra is here to stay!