fix build timeout and missing image type in liminal yaml

diff --git a/liminal/build/image_builder.py b/liminal/build/image_builder.py
index 43b7267..cfc423f 100644
--- a/liminal/build/image_builder.py
+++ b/liminal/build/image_builder.py
@@ -74,7 +74,7 @@
         try:
             docker_build_out = subprocess.check_output(docker_build_command,
                                                        shell=True, stderr=subprocess.STDOUT,
-                                                       timeout=240)
+                                                       timeout=960)
         except subprocess.CalledProcessError as e:
             docker_build_out = e.output
             raise e