feat: add AvlTreeMap data structure

[RIvance]

Description of Change

The comments in data_structures/avltree.cpp mentioned that:

\todo update code to use C++ STL library features and OO structure \warning This program is a poor implementation and does not utilize any of the C++ STL features.

I implemented a full-featured map using AVL Tree and wrote some tests.

Checklist

• [x] Added description of change
• [x] Added file name matches File name guidelines
• [x] Added tests and example, test must pass
• [x] Added documentation so that the program is self-explanatory and educational - Doxygen guidelines
• [x] Relevant documentation/comments is changed or added
• [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.

Notes:

[github-actions[bot]]

This pull request has been automatically marked as abandoned because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[github-actions[bot]]

This pull request has been automatically marked as abandoned because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[RIvance]

Thanks for the feedback! :smiley: All fixed.

[github-actions[bot]]

This pull request has been automatically marked as abandoned because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[RIvance]

Thanks for the review again. All missing docs are added. :slightly_smiling_face:

[RIvance]

All done. :)

[github-actions[bot]]

This pull request has been automatically marked as abandoned because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[github-actions[bot]]

This pull request has been automatically marked as abandoned because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[github-actions[bot]]

Please ping one of the maintainers once you commit the changes requested or make improvements on the code. If this is not the case and you need some help, feel free to ask for help in our Gitter channel or our Discord server. Thank you for your contributions!