Add documentation for Miden crypto

[Dominik1999]

We want documentation for Miden crypto

As described in 0xPolygonMiden/miden-base#472, we want documentation for the Miden crypto. The documentation source files should be located in the crypto repo. Then, developers can update the docs using the same PR as the code.

Target group for the Miden crypto docs

We have different target groups for our documentation:

1. People who want to develop on top of Polygon Miden - e.g., write new smart contracts (accounts, notes), build new applications, etc. For them, they should be able to understand the underlying primitives and trade-offs
2. People who want to contribute to Polygon Miden - e.g., those who may be interested in making proposals to improve the cryptography or contribute to the development etc.
3. People who want to use Polygon Miden. For now, this is mostly people who may want to play with it - but in the future, it can be people who want to participate in running the network.

For now, the order of importance is the above.

Proposed structure

• let's discuss / settle on a structure in this issue

Mkdocs

We are going to use Mkdocs and a plugin to build the Miden unified docs in docs.polygon.technology.

So please build the docs with mkdocs material already in mind.

[bobbinth]

I think the structure could largely follow what we have in the main readme - e.g.,

• Hash functions
• Merkel structures
• Digital signatures

We'll need to write a bit more content for each section (to explain constructions in more detail, as well as motivation and relevance for the Miden rollup) - but other than that, the docs should be fairly straightforward.