Add example Patternkit that adds subpatterns

Problem/Motivation

This allow us to test more varierty to use case where patterns do not load immediately on in the block.

Proposed resolution

- Add the component Multiple Example
- Add test for Multiple Example.

Remaining tasks

- Add component modules/patternkit_example/lib/patternkit/src/components/multiple_example
- Add test for the new component.

User interface changes

- None

API changes

None

Data model changes

None