Add Danger checks

[armcknight]

Some things that come up fairly often in my own development and in code reviews (both things asked for but also missed which lead to confusion later) are if a commit or PR branch contains:

• [ ] changes to a pbxproj or file renames and running synx produces new changes
• [ ] changes to the Podfile and a pod install produces new changes in Pods/, Podfile.lock or the main pbxproj
• [ ] changes to Podfile.lock or Pods/ but not Podfile (maybe others like this for Gemfiles etc)
• [ ] changes to signing team or provisioning profile settings

Thought about suggesting adding as a warning in a precommit hook, but worried about the amount of time it would take to create a commit.