feat: Add Burrows-Wheeler Transform (BWT) implementation in R

[sgindeed]

• Implements Burrows-Wheeler Transform (BWT) for a given string in R.
• Appends a unique end-of-string marker $ to ensure proper rotations.
• Generates all cyclic rotations of the input string.
• Sorts the rotations lexicographically to prepare for BWT.
• Constructs the BWT by taking the last character of each sorted rotation.
• Includes interactive input, allowing users to enter any string.
• Returns a list containing original string, sorted rotations, and the final BWT for easy inspection.

[sgindeed]

@siriak please review and let me know if any modifications are needed

[Copilot]

Pull Request Overview

Adds a complete implementation of the Burrows-Wheeler Transform (BWT) algorithm in R for string manipulation and compression applications. The implementation generates cyclic rotations of an input string, sorts them lexicographically, and constructs the BWT by extracting the last character of each sorted rotation.

• Implements core BWT algorithm with proper end-of-string marker handling
• Provides interactive user input functionality for testing
• Returns comprehensive results including original string, sorted rotations, and final BWT

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[siriak]

Looks good, thanks!