Add Fibonacci prioritization scale up to 13

I want a Fibonacci prioritization scale that goes up to 13 (1, 2, 3, 5, 8, 13). Currently, the 'Fibonacci' option only goes to 8, which is too small for us, and 'Fibonacci+' goes to 21, which is too large and makes the priority chart in /posts difficult to work with. Having an intermediate option would be much better for our workflow.