HostInterface: Add OpenPackageFile method

src/core/host_interface.h

@@ -133,6 +133,10 @@ public:
   /// Returns true if any BIOS images are found in the configured BIOS directory.
   bool HasAnyBIOSImages();
 
+  /// Opens a file in the DuckStation "package".
+  /// This is the APK for Android builds, or the program directory for standalone builds.
+  virtual std::unique_ptr<ByteStream> OpenPackageFile(const char* path, u32 flags) = 0;
+
   virtual void OnRunningGameChanged();
   virtual void OnSystemPerformanceCountersUpdated();