Update mentoria from V5 to V6 (training-center#948)

* Remove old profiles

* Update README

* Add mentors list

* Add templates

* Update mentors-list.md

* Update README.md

* Update mentor-list.template.md

* Create README.md

* Update testimony.template.md

* Update mentor-list.template.md

* Update README.md

* Update README.md

* Update mentor-list.template.md

* Update mentors-list.md

* Create pull_request_template.md