{eval-rst} throws a NotImplementedError with ".. contents::" directive

[tombakas]

Description

Using

```{eval-rst}
.. contents::
```

Inside of a markdown file throws the following exception:

Exception occurred:         
  File "/home/tomas/tmp/venv/lib/python3.8/site-packages/sphinx/writers/html5.py", line 790, in unknown_visit
    raise NotImplementedError('Unknown node: ' + node.__class__.__name__)
NotImplementedError: Unknown node: pending

However, if the following is used instead, no exception is thrown:

```{contents}
```

To Reproduce

1. Set up a virtual environment.
2. Install sphinx and myst-parser using pip.
3. Set up a basic project using sphinx-quickstart
4. Include a markdown file in the toctree of index.rst, let's say test.md.
5. Put the following in the test.md file:

```{eval-rst}
.. contents::
```

6. Try to compile it with make html
7. See error.

Expected behavior

The document compiles without error, the same way it does when the following construction is used:

```{contents}
```

Environment

• Python version: 3.8.7
• Sphinx version: 3.5.1
• Myst parser version: 0.13.5
• Operating system: Fedora 32

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