[5.x] Add get method to Dictionary Item

[ajnsn]

Thank you for the great Dictionary field type.
It replaces so much custom code when dealing with Enums or API calls.

Such "dictionaries" typcially do not have not only value and label . We put a lot of data inside the extra array and need to access it often and repeatedly retrieve this extra data via keys.

Can we get a little get-helper inside the Item class to access the extra data more easily?

[jasonvarga]

Hey! You can already do that via array access:

$item['color'];
$item['colour'] ?? 'red';

If having a dedicated method is really important to you we can reconsider.