Add a page about App Optimization

[michael-hawker]

Now that we have the meta Controls package, we need a Wiki page (or maybe a docs page?) about how a developer can optimize their app by referencing the sub packages for only the controls they need.

Adding this issue as a placeholder for now to point to from our readme.

In general, I think the easiest course of action is for a developer to just remove the reference to the Controls package and see what breaks.

They can then identify which controls they're using that way and add the corresponding NuGet package for them by looking them up in our API docs.

Each control doc's header says which package it is in:

[ghost]

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