Adding files changed to footer in Files section

### Is your feature request related to a problem? Please describe.
I want to see at a glance the files that are changed when I look at the files tab. It gives me a quick gauge on assessing the blast radius of my changes

### Describe the solution you'd like
I want a specific file count as well

### Describe alternatives you've considered
I understand that the counter there helps to count the total files / directories, but they don't really fit my use case

### Additional context
The image shows the number of rows, even though the change file count is actually 1

I have an example for what I want (I have already fixed this locally, but would like to open a PR to hopefully help out others who empathise with my use case) so do let me know if it's an issue anyone else faces and would like.

Start by locating the Files section and its footer in the repository, then trace how the current file or directory count is assembled. Update the footer so it also shows the number of changed files, and verify that the displayed count matches the change shown in the issue's example.

Written by the indexing model from the issue text.