Docs - Reorganize with diataxis

[lucas-tortora]

Description of change

To make all of the Iota docs follow the same top-level structure, the TW and Dev Ex teams are reorganizin the docs.

• Unified examples by action and added tabs per language to make the UI and UX a bit better
• Grouped all explanations, how-tos and references on a top-level folder

I've altered as little text as possible in the PR as the focus is structure.

Type of change

• Documentations Enhancement (a non-breaking change that adds functionality)

How the change has been tested

Wiki was built locally

Change checklist

Tick the boxes that are relevant to your changes, and delete any items that are not.

• [x] I have followed the contribution guidelines for this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation

Pending tasks

• [ ] See if we can add more internal references

[lucas-tortora]

@aleksei-korolev , though I must say I agree with some of the comments, the text isn't the focus of the PR, structure is. If we address both in the same PR the scope will be a bit too big if you ask me

[lucas-tortora]

@mastrogiovanni, @dominic22 could you take a look at this whenever you have a minute?