Remove the recommendation that lines are kept to fewer than 80 characters. We removed the line length check from Rubocop in govuk-lint PR 7 and it feels as though this Styleguide and the Rubocop rules should be kept in sync. : alphagov/govuk-lint#7
This is a wholesale copy of the page on the opsmanual about reviewing external PRs, which I will remove once this commit is on master. It makes sense for this information to be together with our other PR guidance, and it would be better for this to be public rather than on the internal-only opsmanual. There is some overlap between what I am adding here and what is already in place on this page; however, I think it's important to add the information as-is as a straight move and we can then edit the rest of the document later.
These are useful links to other styleguides. This is worth clarifying as it's not clear whether/how they are maintained. Could consider removing them from here. I have not included the external link to the [wiki wiki](https://github.com/alphagov/wiki/wiki) for gem guidelines, as they should be here.