Container directive does not properly contain all contents when attributes are specified.

[Corvimae]

Subject of the issue

I have a container directive that takes an optional argument theme. When I put a list inside the container, it is rendered within the container if there are no attribute braces and outside the container if there are braces and the closing ::: is rendered as text.

Your environment

• OS: macOS Big Sur
• Packages:

  ├─ micromark-extension-directive@1.1.1
  │  ├─ micromark@~2.11.0

• Env: node v15.5.0, yarn 1.22.5

Steps to reproduce

Without attribute braces:

:::card
**Test Content**

- This
- Is
- A
- List
:::

With attribute braces:

:::card{}
**Test Content**

- This
- Is
- A
- List
:::

Expected behavior

Both cards should render the same children.

Actual behavior

The card with attributes does not contain the list, and the closing ::: is rendered as text.

[wooorm]

Thanks, released! https://github.com/micromark/micromark-extension-directive/releases/tag/1.1.2