test: Make sure we have unicode in the SDK tests (#83)

Related to https://github.com/extism/extism/pull/82

Ensures we have unicode inputs in our SDK tests. We should probably get
unicode in the output as well

ruby/test/test_extism.rb

@@ -20,6 +20,8 @@ class TestExtism < Minitest::Test
       assert_equal res["count"], 7
       res = JSON.parse(plugin.call("count_vowels", "this is a test thrice"))
       assert_equal res["count"], 6
+      res = JSON.parse(plugin.call("count_vowels", "🌎hello🌎world🌎"))
+      assert_equal res["count"], 3
     end
   end