document how to save things

(might be useful...)

glsl/docs.js

@@ -79,6 +79,7 @@ Use the sliders on the left to change values used in the shader.
- \`Ctrl-Enter\` reruns the shader
- \`Ctrl-e\` toggles the editor
- \`Ctrl-s\` (in the editor) saves the current shader
- \`Space\` toggles animation
- \`Ctrl-h\` toggles help