Add a hello world example

[hydra]

When I attempted to learn Iced I looked for a hello world example that doesn't have/need/use any kind of state, I just wanted a basic window with some text on it. I did not find such an example, so I made this one.

What was interesting is that the framework forces you to define a Message type and an update method which uses the Message type, but the Hello World case does not have any messages or state. You also have to return something from the update method, again forcing you to use additional types that I didn't expect to have to learn about for a "Hello world" example. i.e. Task.

Hope this helps others looking for a simpler example than the 'Counter' example.

[alex-ds13]

This was already suggested previously. Here is the response of the maintainer: #2434 (comment)

[hydra]

This was already suggested previously. Here is the response of the maintainer: #2434 (comment)

Interesting, happy to note I wasn't the first person looking for one!