Show file content based on first diff

**Is your feature request related to a problem? Please describe.**
When opening lazygit to browse the files in order to see changes made, no changes are shown if the file has more lines than the current terminal and the diff appears after the shown part of the file.

**Describe the solution you'd like**
As a user it would be helpful if the diff is shown right away.

**Describe alternatives you've considered**
To see the change I have to enter the file in order to jump to the diff.

**Additional context**