Second `Text2d` example explaining `Anchor`, `JustifyText` and `TextBounds/Text2dBounds`

# Objective

For drawing and animating short labels `Text2d` is relatively simple and the current `text_2d` example (https://bevyengine.org/examples/2d-rendering/text2d/) demonstrates its basic features well. But there is a lot of confusion about the `Text2d`'s `Anchor`, `JustifyText` and `TextBounds/Text2dBounds` API and there should be a second more technical example that explains precisely how they interact with each other and how they can be used to construct more complex text layouts.