Add lint for intended duplicate content, that would be skipped

[JoshuaBehrens]

I wanted to add some content to a yaml at different places.

To not have the same content duplicated I used yaml pointers. When adding the yaml pointer references at multiple places this line hits: https://github.com/symfony/flex/blob/8ce1acd9842abe0e9b4c4a0bd3f259859516c018/src/Configurator/AddLinesConfigurator.php#L171-L173
It will prevent the additional references to be added as the content is already in the file. It will not print a hint as it is the intended check for a change, that might not have to be applied.

In my case it is intentional and it should be mentioned as early as possible. Therefore I add the check to the manifest lint instead of symfony/flex itself as this will be checked eventually when the recipe has been published already.

Template yaml:

ci.yml

steps:
# steps

trigger:
  branch:
    main:
      # trigger_main
    stage:
      # trigger_stage

Expected result:

 steps:
 # steps
+  - step: &pointer
 
 trigger:
   branch:
     main:
       # trigger_main
+      - step: *pointer
     stage:
       # trigger_stage
+      - step: *pointer

Current result:

 steps:
 # steps
+  - step: &pointer
 
 trigger:
   branch:
     main:
       # trigger_main
+      - step: *pointer
     stage:
       # trigger_stage

I can solve this by having a comment behind the pointer reference usage and to make it unique. But it is such a hassle to debug this until you find this skip so I'd rather be notified about this early :)

 steps:
 # steps
+  - step: &pointer
 
 trigger:
   branch:
     main:
       # trigger_main
+      - step: *pointer # at trigger_main
     stage:
       # trigger_stage
+      - step: *pointer # at trigger_stage