add API documentation to flowlib (part 1)

mods/CORE/flowlib/API.md

@@ -0,0 +1,35 @@
+# flowlib
+Simple flow functions.
+
+## flowlib.is_touching()
+
+
+## flowlib.is_water(pos)
+Return true if node at <pos> is water, false overwise.
+* pos: position
+
+## flowlib.node_is_water(node)
+Return true if <node> is water, false overwise.
+* node: node
+
+## flowlib.is_lava(pos)
+Return true if node at <pos> is lava, false overwise.
+* pos: position
+
+## flowlib.node_is_lava(node)
+Return true if <node> is lava, false overwise.
+* node: node
+
+## flowlib.is_liquid(pos)
+Return true if node at <pos> is liquid, false overwise.
+* pos: position
+
+## flowlib.node_is_liquid(node)
+Return true if <node> is liquid, false overwise.
+* node: node
+
+## flowlib.quick_flow(pos, node)
+* pos: position
+* node: node
+
+## flowlib.move_centre(pos, realpos, node, radius)