add support for hid gamepad interface

add documentation for HID joystick
Add joystick_task to read analog axes values even when no key is pressed or release. update doc
Update docs/feature_joystick.md
Manage pin setup and read to maintain matrix scan after analog read

tmk_core/common/keyboard.c

@@ -71,6 +71,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #ifdef MIDI_ENABLE
 #    include "process_midi.h"
 #endif
+#ifdef JOYSTICK_ENABLE
+#   include "process_joystick.h"
+#endif
 #ifdef HD44780_ENABLE
 #    include "hd44780.h"
 #endif
@@ -396,6 +399,10 @@ MATRIX_LOOP_END:
     }
 #endif
 
+#ifdef JOYSTICK_ENABLE
+    joystick_task();
+#endif
+
     // update LED
     if (led_status != host_keyboard_leds()) {
         led_status = host_keyboard_leds();