Add TimeoutConnector decorator

[clue]

Uses promise cancellation to cancel pending connection attempts after the timer expired.

This means the exposed interface should already work, but the underlying socket resources will not currently be cleaned up in time. As such, it probably makes sense to postpone this until #40 is in. Hence marking this as WIP for now. Edit: See #71

Closes #28, supersedes/closes #10

[WyriHaximus]

LGTM 👍

[clue]

• Rebased to resolve any merge conflicts.
• Updated to support cancellation (see also Support Promise cancellation for all connectors #71)
• Removed WIP marker because it also works without cancellation support (still makes sense to tag this in the same release as Support Promise cancellation for all connectors #71 though)

This is now ready for review

[WyriHaximus]

Awesome, this is a really useful decorator 👍