Add category for rOpenSci internal and peer-review tools

[noamross]

It's good practice for as much of our internal tooling as possible to be subject the standards of RO review, but many of those tools do not strictly fall under any of our categories in Aims and Scope (e.g. ropensci/software-review#671). We should add a category such as

rOpenSci internal tools: packages created and/or used by the rOpenSci team to support software peer review and other related initiatives.

In the review templates, we would add this category with the caveat "(for staff, editor, or pre-approved packages only.)"

@ropensci/editors, give a 👍 / 👎 , comment below!