Solving the `Top k most frequent words` problem using a max-heap

[aparibocci]

Describe your change:

This PR aims to add an algorithm to identify the top k most frequent strings given a provided string list of elements. To do this, the algorithm is using a max-heap implementation already existing in this repository (a generic type was introduced to allow the usage).

Time complexity is O(n), where n is the number of words:

• O(n) for building the max-heap
• k*O(logn) for extracting the k most frequent strings

• [x] Add an algorithm?
• [ ] Fix a bug or typo in an existing algorithm?
• [ ] 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 commit message contains Fixes: #{$ISSUE_NO}.