css-aesthetics into main

Most of the general aesthetic changes have been made in this branch. I have incorporated the changes from the other repository, but have also added a few new things here and there.

Some things to note:

I have temporarily removed the DTOutput for "data_view" under settings (will merge data_view and tbl_view in a new branch)
I haven't added a hex yet - will also add in a new branch
Not sure how you feel about the scrollbar colour in https://github.com/GSK-Biostatistics/tfrmtbuilder/pull/2/commits/3889bfed6e07a26ba2f40f145034f886ccc33366, wasn't sure if it should be orange or blue
The glowing text input box border/button reactivity still works with the bslib theme (yay!)

GSK-Biostatistics / tfrmtbuilder

css-aesthetics into main #2