Add Ruby solution for 2025 day 2 part 1

src/y2025/d02/solve.rb

···
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+ranges = ARGF.read.scan(/(\d+)-(\d+)/).map { |(a, b)| (a.to_i)..(b.to_i) }
+
+puts ranges.flat_map { |range|
+  range.select { |n| n.size.even? && n.to_s.then { |s| s[0...(s.size / 2)] == s[(s.size / 2)..] } }
+}.sum