Allow re-calculation of local IMD rankings

[ThomUK]

Within a certain area, there can be benefit to ranking the LSOAs according to the national IMD rank, and then re-applying local IMD deciles such that each area contains all deciles from 1-10 in an even distribution.

For example, using national IMD the Black Country is skewed towards lower deciles:
https://github.com/ThomUK/imdvizzer#nhs-black-country-integrated-care-board
While Buckinghamshire, Oxfordshire, and Berkshire is skewed towards higher deciles.
https://github.com/ThomUK/imdvizzer#nhs-buckinghamshire-oxfordshire-and-berkshire-west-integrated-care-board

Recalculating a local IMD enables the detail within each area to be more clearly seen.