LibWeb/WebGL: Implement getShaderPrecisionFormat

Author: https://github.com/Lubrsi
Commit: bf2b8c5f2b
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2791
Reviewed-by: https://github.com/gmta
Reviewed-by: https://github.com/shannonbooth

Libraries/LibWeb/Forward.h

@@ -841,6 +841,7 @@ class WebGLProgram;
 class WebGLRenderbuffer;
 class WebGLRenderingContext;
 class WebGLShader;
+class WebGLShaderPrecisionFormat;
 class WebGLTexture;
 class WebGLUniformLocation;
 }