Export GridColorUtils from @deephaven/grid

[gzh2003]

Summary

GridColorUtils is not exported from the @deephaven/grid package's public API. Consumers that need color utilities (e.g., hexToRgb, linearSRGBToOklab, OklabToLinearSRGB, lerpColor, rgbToHex) must import directly from the dist path:

import GridColorUtils from '@deephaven/grid/dist/GridColorUtils';

This bypasses the barrel export and can duplicate code in the built output.

Proposed Fix

Export GridColorUtils from @deephaven/grid/src/index.ts.