Set vertical alignment for SVG in buttons

Makes the buttons in the info panel “tools” tab look more like buttons
on Chrome.

themes/tiddlywiki/vanilla/base.tid

@@ -234,6 +234,10 @@ a.tw-tiddlylink-external:hover {
 ** Buttons
 */
 
+button svg {
+	vertical-align: middle;
+}
+
 .btn-invisible {
 	padding: 0;
 	margin: 0;