To add Implementation of Base64 Algorithm

[NithinU2802]

Description

This PR adds an implementation of the Base64 conversion algorithm in Java. The utility provides methods to encode text into Base64 format and decode Base64 back to the original text, ensuring safe conversion of binary and textual data.

Please let me know if any changes are required. I'm happy to update accordingly 🚀.

This PR closes issue #6585 .

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

❌ Patch coverage is 98.50746% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 75.58%. Comparing base (d8ddb07) to head (7c01f73).

Files with missing lines	Patch %	Lines
...ain/java/com/thealgorithms/conversions/Base64.java	98.50%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6586      +/-   ##
============================================
+ Coverage     75.50%   75.58%   +0.07%     
- Complexity     5688     5722      +34     
============================================
  Files           694      695       +1     
  Lines         19570    19637      +67     
  Branches       3791     3812      +21     
============================================
+ Hits          14776    14842      +66     
  Misses         4217     4217              
- Partials        577      578       +1     

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[alxkm]

Looks good. Thanks for the contribution.