feat: add LeetCode problem 65

[MustafaAamir]

Solution for valid number

Description of Change

Added solution to leetcode 65 (valid number)

• [ x] Added description of change
• [ x] Added file name matches File name guidelines
• [ x] Added tests and example, test must pass
• [ x] PR title follows semantic commit guidelines
• [ x] Search previous suggestions before making a new one, as yours may be a duplicate.
• [ x] I acknowledge that all my contributions will be made under the project's license.

[github-actions]

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