Add CC0 glass textures from default mod...

Source: https://github.com/minetest/minetest_game/tree/master/mods/default

README.md

@@ -1,25 +1,29 @@
 ## Glass Mod for Minetest
 
----
 ### Description:
 
 [Minetest][] mod that makes [default glass nodes][default] colorable with *unifieddyes:airbrush*.
 
 ![screenshot](screenshot.png)
 
---------------
 ### Licensing:
 
-- [MIT](LICENSE.txt)
+- Code:     [MIT](LICENSE.txt)
+- Textures: multiple (see following table)
+
+#### Texture Sources:
+
+| Filename              | Author      | License | Source                   |
+| --------------------- | ----------- | ------- | ------------------------ |
+| glass                 | Krock       | CC0     | [minetest_game][default] |
+| glass_detail          | Krock       | CC0     | [minetest_game][default] |
 
------------------
 ### Dependencies:
 
 Required:
 - [default][]
 - [unifieddyes][]
 
-----------
 ### Links:
 
 - [![ContentDB](https://content.minetest.net/packages/AntumDeluge/glass/shields/title/)][ContentDB]
@@ -31,5 +35,5 @@ Required:
 
 [Minetest]: http://www.minetest.net/
 [ContentDB]: https://content.minetest.net/packages/AntumDeluge/glass/
-[default]: https://github.com/minetest/minetest_game/blob/master/mods/default
+[default]: https://github.com/minetest/minetest_game/tree/master/mods/default
 [unifieddyes]: https://forum.minetest.net/viewtopic.php?t=2178