[Feature] Display selected item count in modal header when editing multiple files

[echo6ix]

Is your feature request related to a problem? Please describe. Uses can select one or multiple cards to edit in grid view using the modal edit window. The modal header pluralizes the noun in the header to signify multiple items are being edited. This subtle visual indication (Edit Scene vs Edit Scenes) could be missed by users unaware that they are editing multiple files.

Describe the solution you'd like Add the number of items being edited in the modal, i.e. Edit scenes (10 scenes)

[elkorol]

This is in my pull request https://github.com/stashapp/stash/pull/4150