Proof of Work Algorithm for Blockchain

[anurags10]

Describe your change:

The algorithm implements the Proof of Work (PoW) consensus mechanism used in blockchain to validate blocks. PoW ensures that participants (miners) must perform a computational task to create a valid block and add it to the blockchain. The difficulty of the task is defined by the number of leading zeros required in the hash of the block.

• [X] Add an algorithm?

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 #ISSUE-NUMBER".

[anurags10]

@tianyizheng02 can you please check and approve it