Add first solution for Project Euler Problem 207 (#3522)

* add solution to Project Euler problem 206

* Add solution to Project Euler problem 205

* updating DIRECTORY.md

* updating DIRECTORY.md

* Revert "Add solution to Project Euler problem 205"

This reverts commit 64e3d36cab2b68630b73a217c9ba455202d85cbb.

* Revert "add solution to Project Euler problem 206"

This reverts commit 53568cf4efd84f4b1c039eade335655842fa29e3.

* add solution for project euler problem 207

* updating DIRECTORY.md

* add type hint for output of helper function

* Correct default parameter value in solution

* use descriptive variable names and remove problem solution from doctest Fixes: #2695

Co-authored-by: nico <esistegal-aber@gmx.de>
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>