Add getFile Action

[jtwebb]

• These actions aren't already listed in the 'All Actions to be implemented' issue here.
• These actions haven't already been requested in another issue.
• Fill out the information below, deleting the examples in italics.

What is the name of the app these actions are a part of?
Shortcuts

Is this a free or paid app?
Free

Please list all of the actions this app exposes.

Provide a link to download a .shortcut file containing as many of these actions as possible.

I'm not sure if I need to do this, the contributing doc is a bit ambiguous. This issue template is setup for different apps, not this library. But the contributing doc still says to open an issue for an action. So here's the issue :) and the pr is #607.