Support for passing a filename to CLI

[kenneth-marut-work]

Feature Description:

With VSCode you can do something like code myfile.txt to open a file from the terminal into VSCode. Similarly, if you run code myfile.txt from an integrated terminal inside VSCode, it will open that file in an editor in the same instance. Would be great to have this behavior inside Theia. This would also allow us to set the git global config core.editor to Theia for users that like to edit commit messages etc. inside the IDE.

[msujew]

@kenneth-marut-work I believe this could be related to https://github.com/eclipse-theia/theia/issues/10890, since using the single instance lock will automatically pass the arguments to the existing Theia instance, were we can handle those appropriately.