Generated documentation and website

[TristanFloch]

The CI executes the following steps to generate the website:

• Install protoc-gen-doc from our GitHub fork and build it. Once our PR merges (Include file reference to types pseudomuto/protoc-gen-doc#522) it would be preferable to switch back to the default installation (using go install).
• Run protoc-gen-doc to generate a multi-paged api-reference under docs/api-reference, using the .github/templates/api-reference-md.tmpl template file.
• Upload an artifact composed of generated api-reference files in case someone wants them.
• Publish the website by pushing to the gh-pages branch using MkDocs Material.

The website can be previewed here: https://aristanetworks.github.io/eossdkrpc.
Local build and preview instructions have been added to the README (that will be public).

The EosSdkRpc HOWTO guide will be added to the documentation on the next PR: #3.

Note: The CI currently publishes the documentation branch instead of main so everyone can have an overview of the generated website. I will change the publishing to master once this PR is approved.

Other note: At the moment, one single workflow file both builds the api reference and deploys the website. It would be preferable to build the api reference on each push, and deploy the website from the main branch only.
A recent GitHub features allows this workflow split in a clean way, but it will only work when workflow files are on the default branch (see documentation note).
My intent is to split workflows after this PR merges.

[bradishp]

While this is not my area of expertise it all looks good to me.

I left some minor NITs and suggestions around the documentation. Once you have addressed those I am happy for this to merge in.