Added suppport for the ONBUILD instruction

Docker-DCO-1.1-Signed-off-by: Asbjorn Enge <asbjorn@hanafjedle.net> (github: asbjornenge)

contrib/syntax/textmate/Dockerfile.tmLanguage

@@ -12,15 +12,37 @@
 	<array>
 		<dict>
 			<key>match</key>
-			<string>^\s*(FROM|MAINTAINER|RUN|CMD|EXPOSE|ENV|ADD)\s</string>
-			<key>name</key>
-			<string>keyword.control.dockerfile</string>
+			<string>^\s*(ONBUILD|)\s*(FROM|MAINTAINER|RUN|EXPOSE|ENV|ADD|VOLUME|USER|WORKDIR)\s</string>
+			<key>captures</key>
+			<dict>
+				<key>0</key>
+				<dict>
+					<key>name</key>
+					<string>keyword.control.dockerfile</string>					
+				</dict>
+				<key>1</key>
+				<dict>
+					<key>name</key>
+					<string>keyword.other.special-method.dockerfile</string>					
+				</dict>
+			</dict>
 		</dict>
 		<dict>
 			<key>match</key>
-			<string>^\s*(ENTRYPOINT|VOLUME|USER|WORKDIR)\s</string>
-			<key>name</key>
-			<string>keyword.operator.dockerfile</string>
+			<string>^\s*(ONBUILD|)\s*(CMD|ENTRYPOINT)\s</string>
+			<key>captures</key>
+			<dict>
+				<key>0</key>
+				<dict>
+					<key>name</key>
+					<string>keyword.operator.dockerfile</string>					
+				</dict>
+				<key>1</key>
+				<dict>
+					<key>name</key>
+					<string>keyword.other.special-method.dockerfile</string>					
+				</dict>
+			</dict>
 		</dict>
 		<dict>
 			<key>begin</key>