Add the connect to box by index trick to SSH docs
Add the connect to box by index trick to SSH docs

Richard towers told me this one during an incident, it was really useful
to stop hopping around between boxes randomly when I had to run a
command across each and didn't know the IP addresses in advance.

Was surprised this wasn't in the docs!

alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs