tidy up method call handler and add example project with camera panning

ios/Classes/filament/FilamentMethodCallHandler.h

@@ -0,0 +1,23 @@
+#ifndef FilamentMethodCallHandler_h
+#define FilamentMethodCallHandler_h
+#endif /* FilamentNativeViewFactory_h */
+
+#import <Flutter/Flutter.h>
+#import "FilamentViewController.h"
+
+#include "FilamentViewer.hpp"
+
+static const id VIEW_TYPE = @"mimetic.app/filament_view";
+
+@interface FilamentMethodCallHandler : FlutterMethodChannel
+- (void)handleMethodCall:(FlutterMethodCall* _Nonnull)call result:( FlutterResult _Nonnull)result;
+- (mimetic::FilamentViewer*) _viewer;
+- (mimetic::ResourceBuffer)loadResource:(const char* const)path;
+- (void)freeResource:(void*)mem size:(size_t)size misc:(void*)misc;
+
+- (instancetype)initWithController:(FilamentViewController*)controller
+                    registrar:(NSObject<FlutterPluginRegistrar>*)registrar
+                    viewId:(int64_t)viewId
+                    layer:(void*)layer;
+
+@end