gitlab-template: Emphasize `user facing` label

My sense is that the current mention of the ~"user facing" label is
overlooked by many MR authors.

Let's move this point up in the list to make it more likely that it is
seen. Also rephrase some of the points.

.gitlab/merge_request_templates/merge-request.md

@@ -5,18 +5,19 @@ expectations. Also please answer the following question in your MR description:*
 
 **Where is the key part of this patch? That is, what should reviewers look at first?**
 
-Please take a few moments to verify that your commits fulfill the following:
+Please take a few moments to address the following points:
 
- * [ ] are either individually buildable or squashed
- * [ ] have commit messages which describe *what they do*
-   (referring to [Notes][notes] and tickets using `#NNNN` syntax when
-   appropriate)
+ * [ ] if your MR may break existing programs (e.g. touches `base` or causes the
+   compiler to reject programs), please describe the expected breakage and add
+   the ~"user facing" label. This will run ghc/head.hackage> to characterise
+   the effect of your change on Hackage.
+ * [ ] ensure that your commits are either individually buildable or squashed
+ * [ ] ensure that your commit messages describe *what they do*
+   (referring to tickets using `#NNNN` syntax when appropriate)
  * [ ] have added source comments describing your change. For larger changes you
    likely should add a [Note][notes] and cross-reference it from the relevant
    places.
- * [ ] add a [testcase to the testsuite](https://gitlab.haskell.org/ghc/ghc/wikis/building/running-tests/adding).
- * [ ] if your MR affects library interfaces (e.g. changes `base`) or affects whether GHC will accept user-written code, please add
-   the ~"user facing" label.
+ * [ ] add a [testcase to the testsuite][adding test].
  * [ ] updates the users guide if applicable
  * [ ] mentions new features in the release notes for the next release
 
@@ -29,3 +30,4 @@ no one has offerred review in a few days then please leave a comment mentioning
 @triagers.
 
 [notes]: https://gitlab.haskell.org/ghc/ghc/wikis/commentary/coding-style#comments-in-the-source-code
+[adding test]: https://gitlab.haskell.org/ghc/ghc/wikis/building/running-tests/adding