Update to ES3 supported.

Working-for-Web-(HTML5).md

@@ -57,6 +57,7 @@ emcc -c raudio.c -Os -Wall -DPLATFORM_WEB
 
 emar rcs libraylib.a rcore.o rshapes.o rtextures.o rtext.o rmodels.o utils.o raudio.o
 ```
+Alternatively to `-DGRAPHICS_API_OPENGL_ES2`, the option `-DGRAPHICS_API_OPENGL_ES3` can also be passed.
 
 The `-Os` flag is used to tell the compiler to optimize code for size, the `-Wall` flag enables all compiler warning messages. Some additional compilation flags can be used (actually provided Makefile defines some more) but they are not required.