Missing optional features

[rwjblue]

The following optional features are missing from /configuring-ember/optional-features/. The prose under each section is directly from the prompt in @ember/optional-features when you run ember feature:enable <feature name>

application-template-wrapper

This will remove the <div class="ember-view"> wrapper for the top-level application template (app/templates/application.hbs).
While this may be a desirable change, it might break your styling in subtle ways:
- Perhaps you were targeting the .ember-view class in your CSS.
- Perhaps you were targeting the <div> element in your CSS (e.g. body > div > .some-child).
- Depending on your choice of rootElement, your app might not be wrapped inside a block-level element anymore.

For more information, see emberjs/rfcs#280.

template-only-glimmer-components

This will change the semantics for template-only components (components without a .js file).
Some notable differences include...
- They will not have a component instance, so statements like {{this}}, {{this.foo}} and {{foo}} will be null or undefined.
- They will not have a wrapper element: what you have in the template will be what is rendered on the screen.
- Passing classes in the invocation (i.e. {{my-component class="..."}}) will not work, since there is no wrapper element to apply the classes to.

While these changes may be desirable for new components, they may unexpectedly break the styling or runtime behavior of your existing components.

To be conservative, it is recommended that you add a .js file for existing template-only components. (You can always delete them later if you aren't relying on the differences.)

For more information, see emberjs/rfcs#278.

[rwjblue]

IMHO, a good start for documenting these would be copying that prose above but I do suspect we'd want some tweaks...