Implements indexing, currently can only be used with strings

tests/integration/IndexTests.cpp

@@ -0,0 +1,14 @@
+#ifdef TESTS_BUILD
+#include <catch.hpp>
+#include "../src/Script.hpp"
+
+TEST_CASE( "String indexing", "[integration]" ) {
+    auto script = Script::Create("'foobar'[4]");
+    REQUIRE(!script->Diagnostics -> HasErrors());
+    script->Evaluate();
+    auto lastValue = script->GetLastValue();
+    REQUIRE(*lastValue->EvaluateString() == "b");
+    delete script;
+}
+
+#endif