Open a local file on the github remote with an optional line number.
Works on macOS.
$ git clone https://github.com/dustbyte/open_github.git
$ ./open_github open_github.sh
# executes `open https://github.com/dustbyte/open_github/blob/main/open_github.sh`
$ ./open_github open_github.sh 14
# executes `open https://github.com/dustbyte/open_github/blob/main/open_github.sh#L14`