Add missing contributor (#4671)

Co-authored-by: Kenneth G. Franqueiro <[email protected]>

Author: iadawn

acknowledgements/ag-wg-active.html

@@ -17,7 +17,7 @@ <h3>Participants of the AG WG active in the development of this document:</h3>
 		<li>Thaddeus Cambron (Invited Expert)</li>
 		<li>Alastair Campbell (Nomensa)</li>
 		<li>Laura Carlson (Invited Expert)</li>
-    	<li>Sukriti Chadha (Invited Expert)</li>
+		<li>Sukriti Chadha (Invited Expert)</li>
 		<li>Rafal Charlampowicz (AccessibilityOZ)</li>
 		<li>Michael Cooper (W3C)</li>
 		<li>Jennifer Delisi (Invited Expert)</li>
@@ -87,7 +87,8 @@ <h3>Participants of the AG WG active in the development of this document:</h3>
 		<li>Kathleen Wahlbin (Invited Expert)</li>
 		<li>Léonie Watson (TetraLogical)</li>
 		<li>Jason White (Educational Testing Service)</li>
-    <li>White, Kevin (W3C Staff)</li>
+		<li>White, Kevin (W3C Staff)</li>
 		<li>Mark Wilcock (Unify Software and Solutions)</li>
+		<li>Todd Libby (Invited Expert)</li>
 	</ul>
 </section>