when config unsafe = false, center-quote without markdown works but shortcode with markdown doesn't work.
the following doesn't work when unsafe = false:
```
{{% center-quote %}}
**hello** *world*
this is a center-quote shortcode example.
{{% /center-quote %}}
```
with this fix, the following works with markdown when unsafe = false:
```
{{< center-quote >}}
**hello** *world*
this is a center-quote shortcode example.
{{< /center-quote >}}
```