run security audit daily at midnight.

[n14little]

This Pull Request fixes/closes #379 .

It changes the following:

• Adds a security audit GitHub action that is scheduled to run nightly at midnight. According to the documentation, a new issue will be created for each advisory.

I ran the audit locally with cargo-audit (what the action uses) and there are not currently any vulnerable packages.

[Razican]

This looks good to me :) could you just add an extra line in the yml file?

[jasonwilliams]

Looks fine to me, echo what @Razican said about the new line

[n14little]

@Razican -- I assumed you meant a new line at the end of the file. Got it added. Let me know if you meant something else and I can address.