README: add hold graph, improve shape gif

README.md

@@ -21,12 +21,14 @@ The following features set it apart from other compressor/limiters:
 #### Adjust the shape of the attack and release.  
   The inspiration for this came from [a video by Dan Worrall](https://youtu.be/7Yit769SN64?t=1115).  
   When shape is at 0, the curve is a slice of pure sine.  
-  ![lamb_shape](https://github.com/magnetophon/lamb-rs/assets/7645711/e49e497a-1cb1-4ce3-b588-917ee1a10afa)
+  ![lamb_shape](https://github.com/magnetophon/lamb-rs/assets/7645711/1cb4e629-a082-47e0-b5e4-755e02a16888)
 #### No discontinuities in the derivative of the gain reduction.  
   The gain never abruptly changes direction, resulting in a smoother sound, even at short attack and release times.
 #### Release hold eliminates distortion while keeping most of the level.  
   It prevents the gain reduction from coming back up if it needs to go down again soon.  
   You control how soon is soon.
+  Here's a graph of the gain reduction with and without hold:
+  ![hold](https://github.com/magnetophon/lamb-rs/assets/7645711/6b11f866-2684-41a4-beb7-f83ea2964246)
 #### Adaptive release (optionally) prevents pumping.  
   When you increase adaptive release, the gain won't rush up when there is a quiet part after a big peak.  
   The first couple of dB of the release will have the speed you set with the release knob, and after that it will slow down.