Resolve "Descriptor in multiple shader stages"

Closes #76 (closed)

include/vkcv/ShaderStage.hpp

 #pragma once
 
 namespace vkcv {
-	
-	enum class ShaderStage
+
+	enum class ShaderStage : uint32_t
 	{
-		VERTEX,
-		TESS_CONTROL,
-		TESS_EVAL,
-		GEOMETRY,
-		FRAGMENT,
-		COMPUTE
+		VERTEX = 0x00000001,
+		TESS_CONTROL = 0x00000002,
+		TESS_EVAL = 0x00000004,
+		GEOMETRY = 0x00000008,
+		FRAGMENT = 0x00000016,
+		COMPUTE = 0x00000032
 	};
-
 }