Added doctests to OddEvenTraposition

[l3str4nge]

Describe your change:

Added missing doctests. Refactor will be in second PR

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

[ruppysuppy]

if arr[i + 1] < arr[i]:
                arr[i], arr[i + 1] = arr[i + 1], arr[i]

can be replaced by:

if arr[i + 1] < arr[i]: arr[i], arr[i + 1] = arr[i + 1], arr[i]

[ruppysuppy]

Suggested change

	for i in range(0, len(arr)):
	for i in range(len(arr)):

[l3str4nge]

This PR is mainly for doctests. Refactoring will be in other as @cclauss suggested before.

[cclauss]

Please change main() to use arr as the variable name instead of shadowing Python’s builtin list.

Perhaps replace the first four lines of main() with:

    arr = list(range(10, 0, -1))

[cclauss]

You already have my approval.

[l3str4nge]

So can I merge?

[cclauss]

Squash and merge