Update documentation.yml (boto#3638)

Add bug label when creating a new document issue.

Author: alikulka

.github/ISSUE_TEMPLATE/documentation.yml

@@ -2,7 +2,7 @@
 name: "📕 Documentation Issue"
 description: Report an issue in the API Reference documentation or Developer Guide
 title: "(short issue description)"
-labels: [documentation, needs-triage]
+labels: [documentation, needs-triage, bug]
 assignees: []
 body:
   - type: textarea
@@ -21,3 +21,4 @@ body:
         Include links to affected documentation page(s).
     validations:
       required: true
+