match: consider guarding against empty text input

[mycargus]

match(text) currently accepts an empty string without raising, which is asymmetric with the empty-pattern guard.

Riteway.match("").call("hello")  # => nil (no error)
Riteway.match("hello").call("")  # => ArgumentError: pattern must not be empty

Passing empty text to match is likely a user bug. The JS riteway does not guard this either, so keeping it unguarded is a defensible choice — but worth a conscious decision.

Options:

1. Add a guard: raise ArgumentError, "text must not be empty" in match(text)
2. Document the asymmetry explicitly and leave it as-is (consistent with JS)