fix: add docs header marker; tests for valueless and empty-literal aria-label

Author: johanrd

docs/rules/template-no-aria-label-misuse.md

@@ -1,5 +1,6 @@
 # ember/template-no-aria-label-misuse
 
+<!-- begin auto-generated rule header -->
 <!-- end auto-generated rule header -->
 
 Flag `aria-label` and `aria-labelledby` on elements whose computed role

tests/lib/rules/template-no-aria-label-misuse.js

@@ -58,6 +58,10 @@ const validHbs = [
   // role per WAI-ARIA §4.1. `role="xxyxyz button"` resolves to `button`,
   // which accepts aria-label — should not flag.
   '<div role="xxyxyz button" aria-label="Custom">x</div>',
+  // Valueless aria-label carries no name — treated as empty, not flagged as misuse.
+  '<div aria-label>x</div>',
+  // Static string-literal mustache — empty string is treated as no label.
+  '<div aria-label={{""}}>x</div>',
 ];
 
 const invalidHbs = [