improvements to jump_search.py

[amirsoroush]

Describe your change:

Here are a few minor improvements to the current implementation of jump_search.py algorithm.

1. int(math.floor(math.sqrt(n))) is the same thing as int(math.sqrt(n)) and it can be calculated once.
2. Better naming for variables.
3. Add type hints which indicates that this function can also work with other sequence types as long as they are comparable.
4. prev = prev + 1 --> prev += 1

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 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".

[tianyizheng02]

Nice improvements