add spartan readme

readme.md

@@ -0,0 +1,25 @@
+# api
+
+note: supports all keys minetest does  
+
+```lua
+controls.register_on_press(function(player, key)
+    -- called on key down
+    -- @player: player object
+    -- @key: key pressed
+end)
+
+controls.register_on_hold(function(player, key, length)
+    -- called while key is held
+    -- @player: player object
+    -- @key: key pressed
+    -- @length: length of time key was held in seconds
+end)
+
+controls.register_on_release(function(player, key, length)
+    -- called on key up
+    -- @player: player object
+    -- @key: key pressed
+    -- @length: length of time key was held in seconds
+end)
+```