Add dictsort filter to @huggingface/jinja

[Copilot]

• [x] Understand the dictsort filter specification from Jinja docs
• [x] Implement the dictsort filter in runtime.ts for ObjectValue
• [x] Add tests for dictsort filter with various parameters
• [x] Test the implementation with edge cases
• [x] Run lint and build to ensure code quality
• [x] Refactor to eliminate code duplication by extracting helper method
• [x] Improve null/undefined handling in sort comparisons
• [x] Add documentation for type handling assumptions
• [x] Move dictsort logic to ObjectValue builtins as FunctionValue per @xenova's feedback
• [x] Extract index calculation to avoid duplication

Original prompt

On jinja, Add support for the dictsort. jinja filter to @huggingface/jinja package. Here are the docs for the feature: https://jinja.palletsprojects.com/en/stable/templates/#jinja-filters.dictsort

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