WEB: Update credits: Haiku maintained by Luc Schrijvers

Quoth Luc Schrijvers (Begasus) on scummvm-devel:
"Haiku is stepping up and there is a recipe (script to build
scummvm) in the haikuporters git repo [...] I'll still do a
full build and make it available for download that could be
upped on your download page when ready"

data/credits.xml

@@ -1371,6 +1371,14 @@
 					<description></description>
 				</person>
 			</group>
+			<group>
+				<name>Haiku</name>
+				<person>
+					<name>Luc Schrijvers</name>
+					<alias>Begasus</alias>
+					<description></description>
+				</person>
+			</group>
 			<group>
 				<name>Mac OS X</name>
 				<person>