Add plugin API write support for TIMING & EASING variable types

[mck]

createVariable and setValueForMode reject the TIMING/EASING variable types, and VariableResolvedDataType / VariableValue don't include them. Reading them already works (resolvedType, valuesByMode) — only writing is missing.

Request

1. Add 'TIMING' | 'EASING' to VariableResolvedDataType
2. Add their value shapes to VariableValue (TIMING = number; EASING = { easingType, bezierValues: { p1x, p1y, p2x, p2y }, springValues? }).
3. Allow createVariable / setValueForMode to accept them at runtime.

figma.variables.createVariable('t', collection, 'TIMING') // and 'EASING'
// ✗ resolvedType failed validation: Expected 'BOOLEAN' | 'COLOR' | 'FLOAT' | 'STRING'

@figma/plugin-typings@1.130.0

[ahurtado-figma]

Thanks for the report! We're tracking internally