This is an empty struct for now, but we will most likely expand on that.
```
[contentTypes]
[contentTypes.'text/markdown']
```
The above means that only Markdown will be considered a content type. E.g. HTML will be treated as plain text.
Fixes#12274
This was recently introduced. so no breaking change.
The thing is:
* We do not commonly use the prefix Default* even if it can be overridden in the templates.
* PagerSize makes more sense and is also the term used in the code.
