feat(react): add hook for font databound properties

[zplata]

With the recent JS runtime support of databinding font properties, adding an equivalent hook similar to the image property hook.

[Copilot]

Pull request overview

Adds a new React hook to support databound font properties on a ViewModelInstance, mirroring the existing image property hook pattern and surfacing it through the public package entrypoints and examples.

Changes:

• Introduces useViewModelInstanceFont hook for setting databound font properties via path lookup.
• Extends public types with RiveDecodedFont / UseViewModelInstanceFontResult and exports the new hook from src/index.ts.
• Adds unit tests and Storybook/example coverage for the new font databinding behavior.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/useViewModelInstanceFont.test.tsx	Adds unit tests covering lookup, setter behavior (including null-clear), and subscription cleanup.
src/types.ts	Defines RiveDecodedFont and the UseViewModelInstanceFontResult type used by the new hook.
src/index.ts	Re-exports useViewModelInstanceFont from the package entry.
src/hooks/useViewModelInstanceImage.ts	Minor docstring clarification for the existing image hook.
src/hooks/useViewModelInstanceFont.ts	Implements the new font property hook using the shared useViewModelInstanceProperty base hook.
examples/src/components/DataBindingTests.tsx	Adds a font databinding example component that decodes a font and sets/clears the property.
examples/src/components/DataBindingTests.stories.tsx	Adds a Storybook story + play assertions for the new font property example.

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[bodymovin]

LGTM