Add GLSL1 and GLSL3 declarations for Typescript

src/constants.d.ts

@@ -365,3 +365,6 @@ export const StreamReadUsage: Usage;
 export const StaticCopyUsage: Usage;
 export const DynamicCopyUsage: Usage;
 export const StreamCopyUsage: Usage;
+
+export const GLSL1: string;
+export const GLSL3: string;