Added docs for sound::loaded_filename and itle_ticks() (#66)

I have added 2 new files according to the docs structure.

doc/src/references/builtin/Audio/Classes/sound/Properties/loaded_filename.md

@@ -0,0 +1,4 @@
+# loaded_filename
+Obtain the path of sound file that has been loaded.
+
+`string sound::loaded_filename;`

doc/src/references/builtin/User Interface/Functions/idle_ticks.nvgt

@@ -0,0 +1,25 @@
+/*
+ Obtain the time passed since a user has pressed a key or used the mouse.
+ uint64 idle_ticks()
+ ## returns
+ Returns the number of milliseconds since a user has not interacted with the machine.
+ ## remarks
+ This function can serve as a useful utility to verify whether a user has been away from the keyboard.
+*/
+
+// Example
+void main()
+ {
+ int64 t;
+
+ show_window("Idle test");
+ wait(50);
+ screen_reader_speak("Press space to check the idle time and escape to exit.", true);
+ while (!key_pressed(KEY_ESCAPE)) {
+ wait(5);
+ if (key_pressed(KEY_SPACE))
+ screen_reader_speak("You have been idle for %0 milliseconds".format(t), true);
+
+ t = idle_ticks();
+ }
+}