Add a ClapPlugin trait

Just like the Vst3Plugin trait

plugins/examples/gain/src/lib.rs

@@ -2,8 +2,8 @@
 extern crate nih_plug;
 
 use nih_plug::{
-    formatters, util, Buffer, BufferConfig, BusConfig, Plugin, ProcessContext, ProcessStatus,
-    Vst3Plugin,
+    formatters, util, Buffer, BufferConfig, BusConfig, ClapPlugin, Plugin, ProcessContext,
+    ProcessStatus, Vst3Plugin,
 };
 use nih_plug::{BoolParam, FloatParam, Params, Range, Smoother, SmoothingStyle};
 use parking_lot::RwLock;
@@ -129,6 +129,8 @@ impl Plugin for Gain {
     }
 }
 
+impl ClapPlugin for Gain {}
+
 impl Vst3Plugin for Gain {
     const VST3_CLASS_ID: [u8; 16] = *b"GainMoistestPlug";
     const VST3_CATEGORIES: &'static str = "Fx|Dynamics";