Fix #12408 Bug fix for empty strings in join.py

[aarthipv]

Describe your change:

• [ ] Add an algorithm?
• [x] 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 #12408 ".

[osman-haider]

@aarthipv your code still have same issue

if we gave input like this

join(",", ["", "", ""])

then we are expecting output like follows

',,'

But your code still returning empty string

[MaximSmolskiy]

@aarthipv Point of this repository is to learn how to implement algorithms and built-in functions yourself, so I can't accept implementation of join function using built-in Python join method

[MaximSmolskiy]

Closed in favor of #12434