Add a test to ensure correct version number format.

Hopefully this will avoid a repeat of the '2.4' debacle...

test/version_test.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+require 'zip/version'
+
+class VersionTest < MiniTest::Test
+  def test_version
+    # Ensure all our versions numbers have at least MAJOR.MINOR.PATCH
+    # elements separated by dots, to comply with Semantic Versioning.
+    assert_match(/^\d+\.\d+\.\d+/, Zip::VERSION)
+  end
+end