Implement branch protection rules

[leopaul36]

GitHub can help us set protected branches.

Unfortunately, this has to be set per repository.

Here is my proposal for tdp-collection (thought it applied to every repo):

[rpignolet]

I agree except for the "Required number of approvals before merging: 2" because, for repo like tdp-lib, tdp-server and maybe tdp-ui we do not have 2 reviewers, for example, for tdp-lib and tdp-server, only @gboutry and me can review the code and can make useful comments. We will be happy if other can review but it is too early to do it in these repositories.

[leopaul36]

We can definitely lower this for particular repositories

[rpignolet]

Ok then.