New example code `mgs_handler`

[rzerres]

Abstract

This example illustrates the usage of massage handling between individual widgets (here: SenderView and ReceiverView).

Context

• msg_handler: the controlling window.
• sender: handle view and state to handle message sending.
• receiver: handle view and state to react when message are passed over.

Context:

A description of the changes proposed in the pull request.

Contribution checklist:

• [X] Add documentation to all public structs, traits and functions.
• [X] Run cargo fmt to make the formatting consistent across the codebase
• [X] Run cargo clippy to check with the linter

[rzerres]

Strange: local : cargo test => all ok! github: cargo test => fails

utils/src/color.rs We do tests for partial_eq, which shoiuld work. assert_eq!(true, Color::rgb(1, 2, 3) == Color::rgba(1, 2, 3, 200)); Color::rgb => 0xFF010203, Color::rgba: => 0xC8010203

But github routine disagrees. help: replace it with: assert!();

but this doen't do what we want.

is this a bug in the github rules?

[FloVanGH]

Looks great so far. Thank you. I'll fix the ci lint later.