Add scale_cubic_bezier expression function, handle bezier-cubic interpolation when converting MapBox styles (Request in QGIS)

[qgis-bot]

Request for documentation

From pull request qgis/QGIS#65701
Author: @nyalldawson
QGIS version: 4.2

** Add scale_cubic_bezier expression function, handle bezier-cubic interpolation when converting MapBox styles**

PR Description:

Description

Complements the existing scale_linear, scale_exponential functions and adds a new bezier-cubic based interpolation method. This is then used when converting MapBox styles using the "cubic-bezier" interpolation type.

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Commits tagged with [need-docs] or [FEATURE]

"[feature] Add scale_cubic_bezier expression function\n\nComplements the existing scale_linear, scale_exponential functions\nand adds a new bezier-cubic based interpolation method.\n\nIntended for use in converting MapBox styles, which heavily\nuse this interpolation technique. Accordingly the implementation\nhas been based off the maplibre native equivalent."