Automatically copy relevant text into user's clipboard

When running commands, eg:

$ git node land --continue
Running `final`..
  ✔  06e09b61712d4963699d90389b43bddcf41c02f0
     ✔  0:0      skipping fixes-url                        fixes-url
     ✔  0:0      blank line after title                    line-after-title
     ✔  0:0      line-lengths are valid                    line-length
     ✔  0:0      metadata is at end of message             metadata-end
     ✔  0:0      reviewers are valid                       reviewers
     ✔  0:0      valid subsystems                          subsystem
     ✔  0:0      Title is <= 50 columns.                   title-length
--------------------------------------------------------------------------------
The following commits are ready to be pushed to DANGER/master
- 06e09b6171 test: refactor http-https-default-ports
--------------------------------------------------------------------------------
To finish landing:
1. Run `git push DANGER master`
2. Post in the PR: `Landed in 06e09b6`
--------------------------------------------------------------------------------
? Clean up generated temporary files? [Y/n] Y

it should be possible to copy the Landed in ... to the clipboard, so the user can just change to browser and directly paste it in.

Not sure if possible on Windows, but on mac it's pbcopy, and on Linux it's normally xclip -selection clipboard.

Beginne damit, die Implementierung und den Ausgabepfad für git node land --continue zu finden, insbesondere die Stelle, an der die Anweisung Landed in ... ausgegeben wird. Ermittle, wie die Unterstützung der Zwischenablage unter macOS, Linux und Windows funktionieren kann; fertig ist es, wenn der relevante Text kopiert wird, damit der Benutzer ihn direkt in den pull request einfügen kann.