Add inventory graphics

CREDITS.md

@@ -18,6 +18,11 @@ Textures:
 - Screwdriver texture: by 12Me21 (CC0)
 - Hotbar textures are a recolored version from from the hotbar textures of the Isabella Texture Pack by Bonemouse (http://www.minecraftforum.net/topic/242175-Isabella/) (CC BY 3.0)
 - `default_dirt.png`, `default_sand.png`, `lzr_core_seabed.png`, `lzr_core_shrub_leaves.png`, `lzr_core_palm_leaves.png`. `lzr_core_palm_leaves_top.png`, `lzr_core_palm_tree.png`, `lzr_core_palm_tree_top.png`: by TheThermos (MIT)
+- `lzr_gui_bg.png`: Based on two works:
+	- 1) <https://opengameart.org/content/sheet-of-old-paper> by Q\_x (CC0)
+	- 2) <https://opengameart.org/content/rpg-gui-construction-kit-v10> by Lamoot (CC BY 3.0)
+- `lzr_gui_button.png`, `lzr_gui_button_hover.png`, `lzr_gui_button_pressed.png`:
+	- Based on <https://opengameart.org/content/rpg-gui-construction-kit-v10> by Lamoot (CC BY 3.0)
 
 Models:
 - Player models comes from Minetest Game (see license of Minetest Game 5.4.1 for details)

mods/lzr_gui/init.lua

@@ -39,9 +39,12 @@ minetest.register_on_joinplayer(function(player)
 		"formspec_version[4]size[11,6.4]label[0.5,0.5;"..F(S("Inventory")).."]list[current_player;main;0.5,0.9;8,4]"
 	)
 	player:set_formspec_prepend([=[
-		listcolors[#5c4432;#a87d5d;#3b2b20;#b75647;#ffffff]
-		bgcolor[#503b2c;false]
-		style_type[button;bgcolor=#5c4432]
+		listcolors[#5c443280;#a87d5d80;#3b2b2080;#b75647;#ffffff]
+		background9[0,0;5,5;lzr_gui_bg.png;true;4]
+		style_type[button;bgimg=lzr_gui_button.png]
+		style_type[button;bgimg_middle=4]
+		style_type[button:hovered;bgimg=lzr_gui_button_hover.png]
+		style_type[button:pressed;bgimg=lzr_gui_button_pressed.png]
 		style_type[button;sound=lzr_sounds_button]
 		style_type[button_exit;sound=lzr_sounds_button]
 		style_type[image_button;sound=lzr_sounds_button]