This is the first of three APIs required to support customized action cell
layouts necessary for internal design guidelines. The `contentEdgeInsets` API
allows configuring the inset/outset values of the content rectangle of each
action cell.
Part of #8709
## Context
As part of our work to move away from _themer_ objects and onto _theming extension_ we need to graduate all of our components theming extensions to the MaterialComponents pod.
## The fix
This PR updates the ActionSheet theming extension to the MaterialComponents pod, as well as updating examples and unit test. Additionally this removes the documentation for _themers_ since they were never out of the MaterialComponentsBeta podspec. The documentation for _themers_ is replaced with documentation for the _theming extension_.
## Bug
Closes#7160
This is an automated change generated by replacing all instances of MaterialComponentsAlpha with MaterialComponentsBeta. This is not a breaking change because changes to Alpha/Beta components (including renaming them) are not considered breaking.
The MaterialComponentsAlpha podspec was mistakenly named Alpha, when what we meant was more close to Beta. The distinction is that Alpha components are not expected to be used by clients, while Beta components are.
### Context
The docs for ActionSheet haven't been updated since the initial PR.
### The problem
There was no section for theming, color or typography theming.
### The fix
Add sections for both color and typography theming to the README.
Before this commit the scrim doesn't have any of the properties needed for accessibility, this will add the functionality that will allow clients to set accessibility properties on the scrim.
Closes#4902
