I got an email receipt for an app I didn’t purchase. How is it possible someone could charge an app purchase to my credit card?

Not likely unless you gave access to your Apple ID to someone else, or you are the family organizer in a Family Sharing group. But then it would not be tied to your Apple ID, but there's.

You can request a refund: link-> Request a refund for apps or content that you bought from Apple - Apple Support

Also, make sure the email is actually form Apple: link-> Identify legitimate emails from the App Store or iTunes Store - Apple Support

If you don't see the charge on your actual payment method, then it may be a scam.

I got an email receipt for an app I didn’t purchase.

The invoice is from Apple?

Click Report a problem.

If the invoice is not from Apple, was the money deducted by a stranger?

Contact your bank, they can find out who (name, address & account number) has collected the amount from your bank account, and when.

Depending on your bank, they can collect the amount back within 30 days.

Ask the bank to block your card, and ask a new card.

Also report to the police.

an app purchase to my credit card and my Apple ID?

See the following Apple articles: 

If you think your Apple ID has been compromised

If you think your Apple ID has been compromised - Apple Support

Personal Safety User Guide

Personal Safety User Guide – Apple Support (UK) 

Security and your Apple ID

Security and your Apple ID - Apple Support

Don't jailbroken your iPhone.