feat(strings): add suffix automaton implementation

[Shrithu10]

Describe your change:

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

This pull request adds an implementation of the Suffix Automaton under strings/suffix_automaton.py.

A suffix automaton is a compact automaton that recognizes all substrings of a given string.
It can be used for:

• Fast substring checks,
• Counting distinct substrings,
• Longest common substring queries, etc.

Time complexity: O(n) for construction.

References:

• https://cp-algorithms.com/string/suffix-automaton.html
• https://en.wikipedia.org/wiki/Suffix_automaton

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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, I will 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.