Support for high precision framebuffers and dither noise (RT64) (#252)

* 64 bit framebuffer for rt64

* Remove mention of motion blur cap from readme

* Add graphics.json option to control high precision framebuffers, disable clamping alpha for accumulation blur when using high precision FBs

* Increase dither noise strength at higher resolutions to make it more noticeable

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Co-authored-by: Mr-Wiseguy <mrwiseguyromhacking@gmail.com>

include/rt64_layer.h

@@ -32,6 +32,7 @@ namespace ultramodern {
             void shutdown();
             void set_dummy_vi();
             uint32_t get_display_framerate();
+            float get_resolution_scale();
             void load_shader_cache(std::span<const char> cache_binary);
         private:
             RT64SetupResult setup_result;
@@ -40,6 +41,7 @@ namespace ultramodern {
     
     RT64::UserConfiguration::Antialiasing RT64MaxMSAA();
     bool RT64SamplePositionsSupported();
+    bool RT64HighPrecisionFBEnabled();
 }
 
 void set_rt64_hooks();