Implement file name emphasis in docs

[shannonbux]

Summary

At the top of code snippets, the file name where they ought to be pasted should be emphasized.

Basic example

Here is the PR that implemented the functionality: #7867
Now we just need to go through the docs and the tutorial (and possibly official plugin and starter READmes?) and use the functionality wherever there is a code snippet that is meant to be pasted into a specific file.

Motivation

In a workshop last May, I noticed that many people paste code snippets into the incorrect file. This way of emphasizing file names will hopefully help everyone paste code into the correct place.

Next steps

If anyone wants to also tackle #5030, that would be an ideal companion issue to tackle along with this one.

[shannonbux]

@DSchau @kakadiadarpan

[DSchau]

@shannonbux 🎉 I'll see if I can find some time to get the copy snippet stuff working. Could be kinda fun to work on!