[gimp] .gitlab: update the merge request template.

[Jehan <jehanp src gnome org>]

commit f86329bb3063d7ca489cfe6e68ceaa4b7be2e66c
Author: Jehan <jehan girinstud io>
Date:   Sun May 31 12:47:47 2020 +0200

    .gitlab: update the merge request template.

 .gitlab/merge_request_templates/default.md | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)
---
diff --git a/.gitlab/merge_request_templates/default.md b/.gitlab/merge_request_templates/default.md
index 71203d7299..aec19627ab 100644
--- a/.gitlab/merge_request_templates/default.md
+++ b/.gitlab/merge_request_templates/default.md
@@ -1,7 +1,12 @@
-Please follow our coding style, which is mostly the GNU coding style
-with some specificities: see [HACKING](HACKING#L123).
+Contribution guidelines:
 
-Also make sure no trailing spaces or tabs are left out.
+- Follow our coding style, which is mostly the GNU coding style
+  with some specificities: see [HACKING](HACKING#L123).
 
-Finally please check the following option when making your request:
-"*Allow commits from members who can merge to the target branch.*"
+- Make sure no trailing spaces or tabs are left out.
+
+- Check the following option when making your request:
+  "*Allow commits from members who can merge to the target branch.*"
+
+- Enable the container registry for your repository:
+  https://docs.gitlab.com/ee/user/packages/container_registry/#enable-the-container-registry-for-your-project