Add loading state to volunteer-headshot component

[joshsmith]

Problem

The volunteer-headshot should have some loading states for async data.

Subtasks

• Add a light gray background for the image as a placeholder, until loaded (keeping in mind that a user may have a transparent PNG, so the background shouldn't remain gray)
• Add a light gray rectangular area for the user's name as a placeholder, until loaded
• Add a light gray rectangular area for the user's role as a placeholder, until loaded

[alistermada]

Is this okay? This was shot while using the mirage fake API with 4 sample users.

[joshsmith]

@alistermada wow sorry for super long delay here. Missed this notification somehow. This looks perfect! Are you ready to submit a PR for it?

[alistermada]

Sorry it's been a while since I worked on this fix. I still need to figure out how to change the tests to make them pass this new code.

[joshsmith]

If you want to push up the changes, then I can give some pointers on how to accomplish that.

[joshsmith]

Opening a PR is a good first step so we can start the conversation around it.