[general] moving ios and android project under ./platform folder

platform/android/src/string_util.cpp

@@ -0,0 +1,25 @@
+#include <mbgl/util/platform.hpp>
+#include "attach_env.hpp"
+#include <jni/jni.hpp>
+
+namespace mbgl {
+namespace platform {
+
+std::string uppercase(const std::string& str) {
+    auto env{ android::AttachEnv() };
+    jni::Local<jni::String> value = jni::Make<jni::String>(*env, str.c_str());
+    static auto toUpperCase = jni::Class<jni::StringTag>::Singleton(*env).GetMethod<jni::String()>(*env, "toUpperCase");
+    auto result = value.Call(*env, toUpperCase);
+    return jni::Make<std::string>(*env, result);
+}
+
+std::string lowercase(const std::string& str) {
+    auto env{ android::AttachEnv() };
+    jni::Local<jni::String> value = jni::Make<jni::String>(*env, str.c_str());
+    static auto toLowerCase = jni::Class<jni::StringTag>::Singleton(*env).GetMethod<jni::String()>(*env, "toLowerCase");
+    auto result = value.Call(*env, toLowerCase);
+    return jni::Make<std::string>(*env, result);
+}
+
+} // namespace platform
+} // namespace mbgl