move tile-grid rendering to pluglet

[ntno]

Description

57 - if md_in_html is enabled, render tile captions using markdown

link to #13 documentation upcoming

References

https://docs.python.org/3/library/unittest.mock.html https://www.geeksforgeeks.org/python-debugger-python-pdb/

Testing

• [x] This change adds test coverage for new/changed/fixed functionality

Checklist

• [ ] I have added documentation for new/changed functionality in this PR or in mkdocs-terminal/documentation
• [x] All active GitHub checks for tests, formatting, and security are passing