Add prettier configuration to format vue/ts files

[jacobtylerwalls]

I'd love to get a .prettierrc in place as soon as possible so we can standardize on:

• single vs. double quotes
• 2 vs. 4 spaces
• line-length

And have a github action step fail PRs that haven't been formatted. Then we can socialize the knowledge about how to configure "format on save" in VS Code so that you never have to hand-format again. (Separately, I'll suggest doing the same thing with the python backend because we seem to get lots of PRs with unrelated formatting changes on a regular basis...)

I don't have a strong preference about quote or indentation width myself.

Originally posted by @jacobtylerwalls in archesproject/arches-docs#394 (comment)