feat: Add config option for the notification timeout duration

[kitsunenokenja]

Re-created PR per maintainer's request.

This change enhances the default setting of 3000 milliseconds for the notification timeout by making the value a user config option.

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This change is 

[CLAassistant]

All committers have signed the CLA.

[JFreegman]

Reviewed 6 of 6 files at r1.
Reviewable status: 0 of 1 approvals obtained

[JFreegman]

@kitsunenokenja You'll need to sign your commit before it can be merged.

[JFreegman]

You used the -s option (sign off) instead of -S (sign with gpg key)

[kitsunenokenja]

If this last update didn't work I'll revisit later to work out the settings for GPG signing.

[JFreegman]

We still can't merge because you haven't uploaded your public key to github in order to verify your signatures. I know it's annoying, but you only have to set it up once. See: https://help.github.com/articles/adding-a-new-gpg-key-to-your-github-account/

[kitsunenokenja]

I already use GPG signing with the Gentoo project here on GitHub. Now I need to sort out the config for working with -S on another repo. I'll amend again as soon as I can.

[kitsunenokenja]

@JFreegman, sorry for the delay! I believe this is ready now.