docs/machine_CAN: Add CAN docs. - #12330

As mentioned on #12331, we want to design a different cross-platform API for machine.CAN . The explanation and plan for this work can be found in #12337.

@IhorNehrutsa How do you feel about closing this docs PR for now? We'll refer to it when drafting the new API, but closing this and keeping #12331 open will make it easier for other folks to find CAN-related driver code that they can build and use.

@projectgus
In any case, we need a PR with machine.CAN docs in addition to the issue New machine.CAN driver #12337.
I would be happy if this PR is used as a starting point for a new PR.
I will close this PR in favor of a new machine.CAN docs PR.

New machine.CAN docs and common bindings were added in 0225704

So I'll close this PR. But thanks for your efforts @IhorNehrutsa .