Circuitry sample for PS/2 Mouse (qmk#3959)

Added a sample circuitry for handling the connection of a PS/2 Mouse.
    Even if it's written that a circuitry is needed, there're a lot of other
    things and the information gets lost really fast. A really simple sample
    helps to remember who wants to implement the functionality about the
    circuitry.

docs/feature_ps2_mouse.md

@@ -6,6 +6,24 @@ To hook up a Trackpoint, you need to obtain a Trackpoint module (i.e. harvest fr
 
 There are three available modes for hooking up PS/2 devices: USART (best), interrupts (better) or busywait (not recommended).
 
+### The Cirtuitry between Trackpoint and Controller
+
+To get the things working, a 4.7K drag is needed between the two lines DATA and CLK and the line 5+.
+
+```
+
+          DATA ----------+--------- PIN
+                         |
+                        4.7K
+                         |
+MODULE    5+  --------+--+--------- PWR   CONTROLLER
+                      |
+                     4.7K
+                      |
+          CLK   ------+------------ PIN
+```
+
+
 ### Busywait Version
 
 Note: This is not recommended, you may encounter jerky movement or unsent inputs. Please use interrupt or USART version if possible.