Created Unassigned: Hierarchy or filter in example browser [10147]

The number of examples are growing, and there will probably be more...
Currently there is only one level in the hierarchy and the list of folders is long.

I suggest to reduce the number of top level folders:

* Showcases - a few examples to show some of the functionality of the library
* Annotations - sub folders for each annotation type
* Axes - sub folders for each axis type
* Series - sub folders for each series type
* Discussion - examples from discussions
* Open issues - examples related to open issues
* Solved issues - examples related to closed issues

An alternative could be to add filtering/tag/search functionality, then we could probably get rid of the hierarchy?
```
[x] Show case
[x] Annotations
[ ] Axes
[ ] Series
[ ] Discussion
[ ] Open issue
[ ] Solved issue
Search for [_______] (search tags, title, subtitle)
```