Add pattern test for trailing newline

[Zac-HD]

Follow-up to #282, since I left it out there: ^abc$ should match abc but not abc\n. This is a useful test because both will match in Python, absent special handling such as js-regex.

[awwright]

Does Python default to multiline matching?

ECMAScript does not:

"abc\n".match(/abc$/);
null
"abc\n".match(/abc$/m);
[ 'abc', index: 0, input: 'abc\n', groups: undefined ]

Aside, what if someone wants to do a multiline match?

[Zac-HD]

Python doesn't default to multiline matching, but for reasons I won't pretend to understand has the behaviour above. Python's equivalent of ECMAScript $ is \\Z, so js-regex can translate but IMO it's a good idea to have an upstream test for this.

The JSON-schema spec does not give any way to use multiline mode, so you'd need to include newlines (or whatever else) in your pattern.