Add moment.js for date related things (#50)

Fix saving

Use mixin everywhere

Format attachment dates

Add format date mixing

Use moment js on task list page

Use moment js on home page tasks

Add moment js

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/50

src/styles/components/tasks.scss

@@ -33,7 +33,8 @@
       display: inline-block;
       cursor: pointer;
 
-      .tasktext {
+      .tasktext,
+      &.tasktext {
         vertical-align: top;
         white-space: nowrap;
         text-overflow: ellipsis;