[Web] Fix Web Editor plugin being added to SCons multiple times

Move the Web Editor plugin files to an editor sub-folder inside the
platform folder.

platform/web/web_main.cpp

@@ -38,6 +38,10 @@
 #include "scene/main/scene_tree.h"
 #include "scene/main/window.h" // SceneTree only forward declares it.
 
+#ifdef TOOLS_ENABLED
+#include "editor/web_tools_editor_plugin.h"
+#endif
+
 #include <emscripten/emscripten.h>
 #include <stdlib.h>
 
@@ -104,6 +108,10 @@ void main_loop_callback() {
 extern EMSCRIPTEN_KEEPALIVE int godot_web_main(int argc, char *argv[]) {
 	os = new OS_Web();
 
+#ifdef TOOLS_ENABLED
+	WebToolsEditorPlugin::initialize();
+#endif
+
 	// We must override main when testing is enabled
 	TEST_MAIN_OVERRIDE