Add Coaches Poll rankings to NCAAF

[smitsam555]

Is your feature request related to a problem? Please describe.
Users should be able to pull the Coaches Poll rankings from the ncaaf.rankings module for each college football season, along with the AP and CFP rankings which are currently supported. The Coaches Poll has a level of popularity and prominence near that of the AP and CFP rankings, and therefore is likely to be desired by many users. If implemented, the ncaaf.rankings module would then support all three college football rankings available on sports-reference.com. These rankings should function similarly to the AP and CFP rankings which are already available.

Describe the solution you'd like
The rankings should be incorporated with the ncaaf.rankings module and be requested and structured similarly to how the AP and CFP rankings are currently handled. As the AP and CFP rankings are provided through separate classes, a third class for the Coaches poll would need to be added.

Describe alternatives you've considered
An alternative to pulling these three rankings using three near-duplicate classes would be to refactor the current code to construct one Rankings class and then have each of three classes for the separate polls inherit from it. Each of these subclasses would just need to use their own respective URLs and perhaps some unique HTML tags. This change would take more work up front, but may be easier to maintain down the road.

Additional context
A link to the 2023 Coaches poll can be found here