* **What does this PR do?**

* **Screenshots (if relevant)**

* **Does this PR meet the acceptance criteria?** (This is just a reminder for you,
  this section can be removed if you fulfill it.)

   - Documentation created/updated (you have to edit
     [doc/manual.xml.head](https://www.github.com/neomutt/neomutt/blob/master/doc/manual.xml.head)
     for that)

   - All builds and tests are passing

   - Added [doxygen code documentation](https://neomutt.org/dev/doxygen)
     [syntax](http://www.stack.nl/~dimitri/doxygen/manual/docblocks.html)

   - Code follows the [style guide](https://neomutt.org/dev/coding-style)

* **What are the relevant issue numbers?**
