Add more GLFW_NO_API documentation

docs/context.dox

@@ -80,6 +80,14 @@ when writing a command-line only application.  The menu bar setup can be
 disabled with a [compile-time option](@ref compile_options_osx).
 
 
+@subsection context_less Windows without contexts
+
+You can disable context creation by setting the
+[GLFW_CLIENT_API](@ref window_hints_ctx) hint to `GLFW_NO_API`.  Windows without
+contexts may not be passed to @ref glfwMakeContextCurrent or @ref
+glfwSwapBuffers.
+
+
 @section context_current Current context
 
 Before you can make OpenGL or OpenGL ES calls, you need to have a current