adding negative binary base conversion algorithms

[meg-1]

Describe your change:

Adding two negative binary base conversion algorithms:

• decimal to negative binary base conversion
• negative binary base to decimal conversion

more about negative binary base: link

• [x] Add an algorithm?
• [ ] Fix a bug or typo in an existing algorithm?
• [ ] 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.
• [x] 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".

[meg-1]

Two commits can't be addressed in one PR.

Hi! Thank you for your feedback.

Did you mean that two different files cannot be addressed in one PR? If so, then, the reason I put these two files in one PR is for time efficiency (for reviewers to not check both files in different PR's), and convenience, due to the fact that they are directly related.

What are your thoughts about that? Would you recommend I separate them, considering the above information, or keep them like they are?