Add the ability to check the merge strategy of merged Pull Requests

Currently, it's not possible to see the merge strategy of merged Pull Requests in Bitbucket Cloud. 

• Since the user has the ability to choose which merge strategy they are using, once the PR is merged, we should be able to capture what merge strategy the user selected for the merge and display that on the merge commit. 

When the user merges changes locally and pushes them to BB, all we know is if those changes already exist but we do not know which strategy is used. So maybe we can show "merged outside of BB" or nothing at all.