Set 'master' branch to 'protected', once created

[vcgeers]

Following discussion at MIRI Software telecon of Dec 7th, we'd recommend setting the 'master' branch to be a 'protected' branch, to disable force-pushes and the associated risk of losing work.

This can be done by going to "Settings" > "Branches" > "Protected Branches" and then add "master" to it. This can only be done once this repo has been initialised and a 'master' branch has been created.

[vcgeers]

Hi Jane,

Now that this repo has been populated, would you like us to mark the master branch as protected, to avoid any risk of force pushes?

[vcgeers]

Noticed this was still open. @jemorrison, would you prefer the master branch to be set to protected?
If not, then we'll leave it as is, and close the issue.

[jemorrison]

I am not sure I really care either way. You can go ahead and mark the master branch protected. If I encounter any problems with it mark protected I will let you know