Add more documentation for loading components

[sshein]

Feature Request

• [x] I’ve searched for any related issues and avoided creating a duplicate issue.

This update is for:

• [ ] Content styleguide
• [x] Component
• [ ] Pattern
• [ ] Utility
• [ ] Other

What is the name

https://design.va.gov/components/loading-indicators

What is the nature of this update?

• [ ] How to build this component/pattern
• [x] When to use this component/pattern
• [ ] When to use something else
• [ ] Usability guidance
• [ ] Accessibility
• [ ] Implementation
• [ ] Research insights
• [ ] Package information

Additional Context

It would be great if there was more guidance in our design system regarding loading spinners - e.g. what should the copy say in various circumstances? How long should we allow a user to wait before we throw up an error? What's a standard pattern for loading after a user has clicked "submit" on a form versus simply waiting for a section of a page to load?

[caw310]

Discussed in design council meeting. This is in the DST backlog with low priority.