Textode

You can see this update summary in 1

Fixes:
- Fix `BackNode` doesn't works with `MultiNode`.

Adds:
- Nothing :(

Docs:
- Remove inconsistency between examples.

Adds:
- New node type `MultiNode`. Can be helpful when you need to send more than one message at once.

Docs:
- Add example for new node type `MultiNode`

Adds:
- `ImageNode` for sending user an image

Internal:
- Add schemas to examples

New node - `FuncNode`