[YazanBrijawi]

Adds use_full_strings.cpp to the strings folder.

• LowerAllString, Split, JoinString and ReplaceWord
• Documented with Doxygen comments and self-tests (assert)
• Compiled and tested locally with g++ -std=c++17 -Wall

Description of Change

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: