Add note about job output scope (#47858)

Co-authored-by: Siara <[email protected]>

data/reusables/actions/jobs/section-defining-outputs-for-jobs.md

@@ -6,6 +6,12 @@ Job outputs containing expressions are evaluated on the runner at the end of eac
 
 To use job outputs in a dependent job, you can use the `needs` context. For more information, see "[AUTOTITLE](/actions/learn-github-actions/contexts#needs-context)."
 
+{% note %}
+
+**Note:** `$GITHUB_OUTPUT` is shared between all steps in a job. If you use the same output name in multiple steps, the last step to write to the output will override the value. If your job uses a matrix and writes to `$GITHUB_OUTPUT`, the content will be overwritten for each matrix combination. You can use the `matrix` context to create unique output names for each job configuration. For more information, see "[AUTOTITLE](/actions/learn-github-actions/contexts#matrix-context)."
+
+{% endnote %}
+
 ### Example: Defining outputs for a job
 
 {% raw %}