Add statusbar component for version control change counts

[sharpenedblade]

Description

Add a component to show the amount of lines added/modified/removed from version control in the statusline. This would look like +4 -3 ~1 in the statusline if 4 lines were added, 3 lines were removed, and 1 line was modified. Helix already shows this information in the gutter, so the status line component just needs to add this up and display it. It would also be nice if this only appears when in a git repository.

Use Case

This lets people see how much they changed in the current file quickly. This feature in VSCode and neovim helps me know how much the current file has changed since the last commit without having to scroll though the entire file, and it would be nice to have it in helix.