Add anchor points to post list page

* post-year now has anchor point, you can click on it or input url with hash tag to jump to a specific year.
* See #39

assets/js/main.js

@@ -86,6 +86,12 @@ if (header !== null) {
   listen('#img-btn', "click", showImg);
   listen('.bg-img', "click", hideImg);
 
+  document.querySelectorAll('.post-year').forEach((ele)=> {
+    ele.addEventListener('click', () => {
+      window.location.hash = '#' + ele.id;
+    });
+  });
+
   window.addEventListener('scroll', throttle(() => {
     autoHideHeader();