fix : sr only mixin behavior

Author: francoistibo

src/scss/abstract/_m-sr-only.scss

@@ -29,6 +29,7 @@
 */
 
 @mixin sr-only($focusable: false) {
+    position: absolute;
     width: 1px !important;
     height: 1px !important;
     padding: 0 !important;