Add Beginner Friendly Examples

[nelsonic]

At present #efc23154 this repo is a good start but it does not have any code.
Our objective with any learn-xyz repo is to make it first place a person needs to go for learning that topic. E.g: https://github.com/dwyl/learn-elixir has everything the person needs to start learning Elixir including the syntax/semantics and code examples.

I propose that we:

• re-work this repo such that all code examples can be run offline provided the reader has the Dart VM installed on their computer OR
• alternatively if they are using a computer that cannot install Dart (e.g. a Chromebook or iPad), we provide links to examples on Dart Pad so they can run and play with the code online.

[nelsonic]

This looks good but it's quite old: https://youtu.be/OLjyCy-7U2U

[nelsonic]

Tensor programming "Introduction to Dart for Beginners - Types, Variables, Functions and Objects - Part One": https://youtu.be/8F2uemqLwvE

[nelsonic]

Which of these two looks more friendly and "professional":

vs:

Using a header image with the Dart Logo I made in "Paint" in less than 2 minutes:

Which one would you read?

[nelsonic]