How to avoid the User to enter atleast 20 Letters (characters) in the Description Field?

How to avoid the User to enter atleast 20 Letters (characters) in the Description Field?

Is it possible to avoid the User to submit the request without entering minimum 20 Letters (characters) in the Description Field? We want to prompt the Warning message for the User to Enter Atleast 20 letters so that the request can be submitted (stop form submission)

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