fix: typos correction in documentation across multiple modules

[cypherpepe]

This PR fixes typographical errors in several README files across the repository:

• Corrected repeated word "an an" to "an" in README.md for Kronecker product.
• Fixed incorrect article "a" to "an" in README.md for Fast Root.
• Resolved typo "optmizes" to "optimizes" in README.md for Levenshtein distance.

Pull Request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build-related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Typographical errors in several documentation files, reducing readability and professionalism.

What is the new behavior?

Improved clarity and correctness in the documentation by fixing the following typos:

• an an → an
• a arbitrary → an arbitrary
• optmizes → optimizes

Does this introduce a breaking change?

• Yes
• No

Other information

No functional changes were made; this PR focuses purely on documentation updates.