Update AUTHORS and DONORS list

New contributors added to AUTHORS:
@hinlopen, @naithar, @rrcore, @SkyLucilfer, @TwistedTwigleg

Thanks to all contributors and donors for making Godot possible!

---

Also changes to relevant code that parses the DONORS.md to match
the new tiers.

doc/classes/Engine.xml

@@ -34,7 +34,7 @@
 			</return>
 			<description>
 				Returns a Dictionary of Arrays of donor names.
-				{[code]platinum_sponsors[/code], [code]gold_sponsors[/code], [code]mini_sponsors[/code], [code]gold_donors[/code], [code]silver_donors[/code], [code]bronze_donors[/code]}
+				{[code]platinum_sponsors[/code], [code]gold_sponsors[/code], [code]silver_sponsors[/code], [code]bronze_sponsors[/code], [code]mini_sponsors[/code], [code]gold_donors[/code], [code]silver_donors[/code], [code]bronze_donors[/code]}
 			</description>
 		</method>
 		<method name="get_frames_drawn">