add priority support

[20k-ultra]

I said to myself I don't want this thing to have priorities but....if we add support to set the priority of a todo we can just print it in a different colour. That makes the feature useful without adding more cognitive overhead for the user. These may also be asked if we need to still remember more frequently like 5 days instead of 15 days.

Example:

rmbrs todos add -p1 "fix issue 123"
rmbrs todos add -p2 "test bug 567"
rmbrs todos add -p3 "cut grass"
rmbrs todos add "rake yard" <--- same priority as p3