Touchscreen: Allow mods to swap the meaning of short and long taps (punch with single tap) (#14087)

This works through a new field "touch_interaction" in item definitions.
The two most important use cases are:
 - Punching players/entities with short tap instead of long tap (enabled by default)
 - Making items usable that require holding the place button (e.g. bows and shields in MC-like games)

doc/android.md

@@ -9,8 +9,8 @@ due to limited capabilities of common devices. What can be done is described bel
 While you're playing the game normally (that is, no menu or inventory is
 shown), the following controls are available:
 * Look around: touch screen and slide finger
-* Tap: Place a node
-* Long tap: Dig node or use the held item
+* Tap: Place a node, punch an object or use the selected item (default)
+* Long tap: Dig a node or use the selected item (default)
 * Press back: Pause menu
 * Touch buttons: Press button
 * Buttons:

doc/lua_api.md

@@ -8787,6 +8787,20 @@ Used by `minetest.register_node`, `minetest.register_craftitem`, and
     -- Otherwise should be name of node which the client immediately places
     -- upon digging. Server will always update with actual result shortly.
 
+    touch_interaction = {
+        -- Only affects touchscreen clients.
+        -- Defines the meaning of short and long taps with the item in hand.
+        -- The fields in this table have two valid values:
+        -- * "long_dig_short_place" (long tap  = dig, short tap = place)
+        -- * "short_dig_long_place" (short tap = dig, long tap  = place)
+        -- The field to be used is selected according to the current
+        -- `pointed_thing`.
+
+        pointed_nothing = "long_dig_short_place",
+        pointed_node    = "long_dig_short_place",
+        pointed_object  = "short_dig_long_place",
+    },
+
     sound = {
         -- Definition of item sounds to be played at various events.
         -- All fields in this table are optional.