Add Slide Direction Enum to Control Slide-In and Slide-Out Direction on `RotateAnimatedText`

[fauziridwan1709]

Summary

This pull request addresses Issue #323, where I propose adding a new enum, SlideDirection, to the RotateAnimatedText widget in the Animated-Text-Kit Flutter package. This enhancement allows users to specify the direction of slide-in and slide-out animations for text, providing greater flexibility and customization options.

Changes Made

• Introduced the SlideDirection enum at the top of the RotateAnimatedText file, enabling users to choose the slide direction.
• Modified the RotateAnimatedText constructor to accept a slideDirection property, allowing users to specify the desired slide direction when creating an instance of RotateAnimatedText.
• Updated the initAnimation method to use the slideDirection property to determine the slide direction for both slide-in and slide-out animations.
• Ensured that the default behavior matches the current behavior for existing users who don't specify a slideDirection.

Testing Done

• Tested the new slideDirection property with various values to ensure that the slide animations behave as expected.
• Ensured that existing functionality remains unaffected by this change.

Screenshots

Working on it.

Closes Issues

Closes #323

Checklist

• [x] I have read and followed the Contributing Guidelines.
• [x] I have tested the changes locally and verified that they work as intended.
• [x] The code adheres to the project's coding style and conventions.

Notes

Please tell if anything else needs to be added - Like flutter documentation, etc.