Add binary to gray code conversion algorithm under Hacktoberfest 2025

[Craniace]

Describe your change:

• [x] Add an algorithm
• [ ] Fix a bug or typo in an existing algorithm
• [x] Add or change doctests — Note: Please avoid changing both code and tests in a single pull request
• [ ] Documentation change

Checklist:

• [x] I have read CONTRIBUTING.md
• [x] This pull request is all my own work -- I have not plagiarized
• [x] I know that pull requests will not be merged if they fail the automated tests
• [x] This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms
• [x] All new Python files are placed inside an existing directory
• [x] All filenames are in all lowercase characters with no spaces or dashes
• [x] All functions and variable names follow Python naming conventions
• [x] All function parameters and return values are annotated with Python type hints
• [x] All functions have doctests that pass the automated testing
• [x] All new algorithms include at least one URL that points to Wikipedia or another similar explanation
• [ ] If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER"