feat!: rename description slot to content in UiModal and focus …

…to the first focusable element to directive `focus-trap` (#507)

* feat: UiModal: add slot#content, change focus for elements inside modal, create story

* feat: fix focus order for actions buttons

* feat: add styles for story

* feat: add suggestions from CR

* change code according to CR suggestions

* feat: add errors to the input in modal and fix focus

* feat: add focus and errorMessage to story with Textarea