Fix doc

[LanaTodorovic93]

Implements suggestions by @raoanirudh

• [x] solve issues with formatting.
• [x] move secondary-perils.txt to underlying science
• [x] work on the corresponding input and output rst files

[CatalinaYepes]

Nice improvements @LanaTodorovic93 !

Below a few suggestions:

1. It will be nice to include the Secondary perils in the workflows list. The liquefaction section has been moved the “underlying science”, as it should be, but still, we should reference it somewhere.
2. Since secondary peril Underlying science should be place in a new section for “Secondary perils”.
3. For the output section, it should be nice to indicate in which output file (the name of the output) the probability of liquefaction is stored.