Write introductory documentation

[llucax]

What's needed?

We need a documentation to introduce new users to channels.

Proposed solution

Write a document that explain the basic channels concepts:

• Channels
• Senders
• Receivers
• ?

It should also mention common pitfalls, like messages should be small and serializable even when there is no networking support yet.

Use cases

No response

Alternatives and workarounds

No response

Additional context

No response