add API to add plugin buttons, fixes

src/scripts/today.js

@@ -0,0 +1,11 @@
+api.addButtonToToolbar('go-today', $('<button class="btn btn-xs" onclick="goToday();"><span class="ui-icon ui-icon-calendar"></span> Today</button>'));
+
+window.goToday = async function() {
+    const todayDateStr = formatDateISO(new Date());
+
+    const todayNoteId = await server.exec([todayDateStr], async todayDateStr => {
+        return await this.getDateNoteId(todayDateStr);
+    });
+
+    api.activateNote(todayNoteId);
+};

src/scripts/weight.html

@@ -65,6 +65,8 @@
                 });
             }
 
+            data.sort((a, b) => a.date < b.date ? -1 : +1);
+
             return data;
         });