Allow attribute directives to be added without a value

Then you would be able to add "ngfx-slide-down" as an attribute instead of "ngfx-slide-down='true'" if you don't want any logic inside the attribute.

Look for the directive definitions in the source code, likely in files like ngfx-slide-down.js or similar. Understand how attribute values are currently parsed. Modify the directive to treat a missing value as 'true'. Test by adding the directive without a value to an element and verifying the animation works.

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