Add codepens instead of example Vue components (part 1) (#57)

* Added first three codepens

* feat: replaced custom components with codepens

* fix: updated codepens with descriptive names

* fix: removed unused components

* fix: fixed lifecycle diagram

* fix: updated template syntax with codepen

* fix: moved watchers to codepens

* fix: edited classes, conditional and list chapters

Co-authored-by: ntepluhina <ntepluhina@gitlab.com>

Author: NataliaTepluhina