Color scale constructor for REACH or AGORA colors
Arguments
- initiative
Either "reach" or "agora
- palette
Palette name from `pal_reach()` or `pal_agora()`
- discrete
Boolean indicating whether color aesthetic is discrete or not
- reverse
Boolean indicating whether the palette should be reversed
- ...
Additional arguments passed to discrete_scale() or scale_color_gradient(), used respectively when discrete is TRUE or FALSE
