New: page deletion confirmation modal, a few bugfixes

-All open file-renaming text inputs disappear when switching tabs to avoid some glitches.

-Added modal to confirm removing a file from project.

-Fixed newly introduced glitch with re-deleting a file.

-Fixed glitch with deleting the last open page.
Fixed: a few small bug fixes

-Fixed a display bug with renaming in Firefox

-Streamlined renaming process a little bit and fixed a glitch in the process

-Fixed how the background colour changed for the console