try to detect forgotten echo (or similar) commands

[ghost]

For new checks and feature suggestions

• shellcheck.net (i.e. the latest commit) currently gives no useful warnings about this
• I searched through https://github.com/koalaman/shellcheck/issues and didn't find anything related

Here's a snippet or screenshot that shows the problem:

#!/bin/bash
"this is a random message"

Here's what shellcheck currently says:

Nothing.

Here's what I wanted or expected to see:

Since my script is just a quoted string that also includes spaces, I'd like shellcheck to give me a warning like:
"W: Did you forget to use the echo command?"