content: improve components docs for the alignment property

[brandyscarney]

URL

https://ionicframework.com/docs/api/

Issue Description

The following components have the alignment property documented at these links:

• Checkbox
• Radio
• Toggle

The playground examples currently only demonstrate how the alignment property works horizontally when the label placement is set to stacked. However, they do not show how the alignment property affects vertical alignment with the fixed, start, and end label placements.

We should add examples demonstrating how alignment works vertically, similar to the following, for each component:

<ion-checkbox alignment="start">
  <div class="ion-text-wrap">
    This is a really long label with a lot of text, causing the label to span 
    multiple lines. As a result, the checkbox will be vertically aligned in 
    the center, rather than at the start of the label.
  </div>
</ion-checkbox>

Note

This is just one example of how to illustrate the usage. It doesn't have to be exactly like the example provided.