Explain what SSH keys are/their benefits
We should extend the "Adding an SSH key to your account" article with an explanation of what an SSH key is and why it is useful.
It was originally planned to include this as part of the "First Repository" article, but due to that article having a stronger focus on HTTPS now, it is probably better suited for the "Adding an SSH key" article instead.
Deleting a branch is permanent. It CANNOT be undone. Continue?