Fix MWException about passing an array named data to Html::element

Change-Id: Iecb72add123fc05b808da294ca81c07627335733

TimelessTemplate.php

@@ -262,6 +262,13 @@ class TimelessTemplate extends BaseTemplate {
 				unset( $attrs[$k] );
 			}
 
+			if ( isset( $attrs['data'] ) ) {
+				foreach ( $attrs['data'] as $key => $value ) {
+					$attrs[ 'data-' . $key ] = $value;
+				}
+				unset( $attrs[ 'data' ] );
+			}
+
 			if ( isset( $item['id'] ) && !isset( $item['single-id'] ) ) {
 				$item['single-id'] = $item['id'];
 			}