Return a random string matching the given template.
// usage
chance.template('{AA####}')
=> 'ZQ7803'
chance.template('{Aa}-{##}')
=> 'Vr-78'
chance.template('{####}:{####}:{####}')
=> '1628:5987:7803'
The template consists of any number of "character replacement" and "character
literal" sequences. A "character replacement" sequence starts with a left
brace, has any number of special replacement characters, and ends with a right
brace. A character literal can be any character except a brace or a backslash.
A literal brace or backslash character can be included in the output by
escaping with a backslash.
The following replacement characters can be used in a replacement sequence: