Made UniRFRemix a FAP, added a Loader for Main Menu

Requires one change in api_symbols.scv

applications/main/unirfremix_loader/unirfremix_loader_app.c

@@ -0,0 +1,9 @@
+#include <applications/services/loader/loader_i.h>
+
+#define TAG "unirfremix_loader_app"
+
+int32_t unirfremix_loader_app(void* p) {
+    UNUSED(p);
+
+    return 0;
+}