[feature] add support for git worktrees

[KonstantinAxt]

• if worktree is identified we use '--git-dir' instead of '--git-common-dir' flag
• should ignore gitRoot setting if inside worktree git directory

[KonstantinAxt]

@bk201- Hello Dimitry, I don't know if it is the right way to contribute to your project. In our company we use your project a lot and I would like to have support for git worktree's. There is already a PR https://github.com/bk201-/jira-prepare-commit-msg/pull/746 with a working solution. So would be great if you can have look at one of them. 😃

[juno7803]

It would be helpful!