Added Continued fractions (#6846)

* updating DIRECTORY.md

* added continued fractions

* updating DIRECTORY.md

* Update maths/continued_fraction.py

Co-authored-by: Caeden Perelli-Harris <caedenperelliharris@gmail.com>

* Update maths/continued_fraction.py

Co-authored-by: Caeden Perelli-Harris <caedenperelliharris@gmail.com>

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Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Caeden Perelli-Harris <caedenperelliharris@gmail.com>
Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>