Tags aren't honored when a new document is created through the CLI

Consider the following example document with the tags `category-tag` and `another-tag` (the first one should be used [as the category per design](https://hackmd.io/s/how-to-tag-notes)):

```md
---
title: issue_example
tags: category-tag, another-tag
---

blablabla

```

directly created from the CLI:

```sh
printf -- "---\ntitle: issue_example\ntags: category-tag, another-tag\n---\n\nblablabla\n" | hackmd-cli import
```

The **tags** of documents created directly from the CLI are **not honored in HackMD's web UI**. The example document above looks like this on after creation:


The tags are only honored **after the first manual edit** from the HackMD web app. The exact same example document from above on after a manual edit: