Add bold, italic and monospace font styling for HUD text elements (#11478)

Co-authored-by: Elias Fleckenstein <eliasfleckenstein@web.de>

doc/client_lua_api.txt

@@ -1314,6 +1314,8 @@ It can be created via `Raycast(pos1, pos2, objects, liquids)` or
     --  ^ See "HUD Element Types"
         size = { x=100, y=100 },  -- default {x=0, y=0}
     --  ^ Size of element in pixels
+        style = 0,
+    --  ^ For "text" elements sets font style: bitfield with 1 = bold, 2 = italic, 4 = monospace
     }
 ```
 

doc/lua_api.txt

@@ -8447,6 +8447,9 @@ Used by `Player:hud_add`. Returned by `Player:hud_get`.
 
         z_index = 0,
         -- Z index : lower z-index HUDs are displayed behind higher z-index HUDs
+
+        style = 0,
+        -- For "text" elements sets font style: bitfield with 1 = bold, 2 = italic, 4 = monospace
     }
 
 Particle definition