[BUG] Extension does not handle git worktrees correctly

Describe the bug
When getting the .git/config, it assumes that it's in the work directory:
https://github.com/codecov/vscode/blob/f708fe89afd86c740e6c192996fdc9438cfe5613/src/coverage/coverage.ts#L140

If somebody like me is a fan of worktrees, they won't have a .git folder in their workspace. Instead, .git will be a text file containing something like this:

gitdir: /home/rasmus/Projects/repo/main/.git/worktrees/branch

When running the codecov extension in a linked worktree, that has such a .git file in lieu of a directory, that will result in the following error:

 Error: ENOTDIR: not a directory, open '/home/rasmus/Projects/repo/branch/.git/config'

To Reproduce
Steps to reproduce the behavior:

1. Clone a repository
2. Run git worktree add -B branch ../branch
3. Open ../branch in vscode with the codecov extension enabled

Expected behavior
The codecov extension should correctly resolve the git repository, and work as well in linked worktrees as in main worktrees.

Start at src/coverage/coverage.ts around line 140 and reproduce the problem with the listed git worktree steps before opening the linked VS Code workspace. Done means the extension resolves the repository and reads its Git configuration successfully for both linked worktrees and main worktrees.