Add search role’s base concept pointing to HTML spec. Fix #1898 (#1900)

Co-authored-by: James Nurthen <jnurthen@users.noreply.github.com>

Author: thibaudcolas

index.html

@@ -7431,7 +7431,7 @@ <h5>Presentational Role Inheritance</h5>
 					</tr>
 					<tr>
 						<th class="role-base-head" scope="row">Base Concept:</th>
-						<td class="role-base"> </td>
+						<td class="role-base"><abbr title="Hypertext Markup Language">HTML</abbr> <code>[^search^]</code></td>
 					</tr>
 					<tr>
 						<th class="role-related-head" scope="row">Related Concepts:</th>