Describe your change:

Add a new cosine_similarity function to maths/cosine_similarity.py that calculates the cosine similarity between two vectors. Cosine similarity is a widely used metric in information retrieval, text mining, and machine learning to measure how similar two vectors are regardless of their magnitude.

• Add an algorithm?
• Fix a bug?
• Improve an existing algorithm?

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.
• 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.