feat: add LeetCode problem 100

[richvigorito]

Check for tree equivalence

Description of Change

We recursively traverse both trees simultaneously:

If both nodes are NULL, return true.
If only one of them is NULL, return false.
Compare the current node values. If they differ, return false.
Recursively check the left children and right children. Both must be true for the trees to be the same.

This naturally follows the definition of two identical trees.

References

Checklist

• Added description of change
• Added file name matches
• Added tests and example, test must pass. CLICK HERE to run in leetcode
• Relevant documentation/comments is changed or added
• PR title follows semantic
• Search previous suggestions before making a new one, as yours may be a duplicate.
• I acknowledge that all my contributions will be made under the project's license.

Notes: