Created by: petetnt
…for better visualization
The guide text for the Using the grid system" in
modal.md` says
To take advantage of the Bootstrap grid system within a modal, just nest .container-fluid within the .modal-body and then use the normal grid system classes within this container.
But the example itself didn't contain the wrapper.
I also added .bd-example-row
for the wrapper to improve the visualization on of the grid system
Fixes #17898 (closed).