[Documentation] Improve documentation

[enridaga]

I'm going to use this comment to collect the general structure of the documentation and general format issues

General structure

The plan for improving the documentation is the following.
The README will be left as it is since it already gives an overview of what the tool does.
The sections that are going to be added are:

• One section for each format showing concrete examples of triplification in case of different arguments.
• A getting started section showing how to run the project and to start submitting queries (see Add Quickstart to documentation #254)
• A video tutorial section which will collect pointers to videos
• Pointers to the showcases (see Integrate Showcases into documentation #253 )
• Resources as suggested by @enridaga in [Documentation] Improve documentation #201 (comment)
• Details of the implementation, such as: SA components, workflows and instructions on how to contribute (e.g., implementing a new triplifier etc.)
• Examples of CLI options

Format issues

• Remove tables from format examples.
• Code blocks inside table cells inside details section ... some processors seem to not like that (e.g. the one of readthedocs.org)

[enridaga]

I think we can leave this issue for any commit related to improvements in the docs