The inverse of format!(). The format argument is the format string, and the s argument is the string to match the format against.
Examples:
- readf1("Hello, {}!", "Hello, world!")
=> Some("world")
- readf("I hope {} are {}!", "I hope you are doing well!")
=> Some(vec!["you", "well"])
- readf1("Goodbye, {}!", "Hello, world!")
=> None