fix(types): make grid.tickWidth Scriptable

[Yahiro025]

Fixes

Fixes #12320

Summary

grid.tickWidth is scriptable at runtime and documented as scriptable in docs/axes/styling.md, but GridLineOptions.tickWidth was typed as a plain number. That made TypeScript reject valid scriptable callbacks.

This updates the type to Scriptable<number, ScriptableScaleContext>, matching neighboring tick options such as tickBorderDash / tickBorderDashOffset / tickColor.

Changes

• src/types/index.d.ts: GridLineOptions.tickWidth → Scriptable<number, ScriptableScaleContext>

No runtime behavior changes.

Test plan

• Confirmed docs mark tickWidth as scriptable
• Confirmed runtime already accepts a function (per issue report)
• Type-only change; neighboring options use the same Scriptable<..., ScriptableScaleContext> pattern

[Yahiro025]

Closing in favor of the earlier open PR #12321, which already fixes #12320 (and covers indexable tickWidth plus type regression tests). Sorry for the duplicate.