Fixed-position header for modal-overflow

[brianmhunt]

It would be quite awesome if modal headers could be (optionally) fixed-position when modals are overflow. When a user scrolls, the header would remain at the top.

Similarly, fixed position footers could also be handy.

It would look like this

[ Header ]
Some content that
spans across multi-
ple lines.

...

As the user scrolls, instead of disappearing the header would remain in the fixed position at the top:

[ Header ]
ple lines.

...

The implementation would – unless I misunderstand – really be just setting the .modal-footer or .modal-header CSS to have position: fixed, and then add some padding at the top or bottom in the amount of the height of the header or footer, respectively.

It may be possible that Bootstrap Affix could be useful here, but I haven't given it too much thought yet.

What do you think, Jordan?

Cheers :beers: