add event templates with image backgrounds

frontend/src/assets/previews/angle_person_event_left.png

frontend/src/assets/previews/angle_person_event_right.png

frontend/src/assets/previews/base_person_event.png

frontend/src/assets/previews/right_person_event.png

.../src/assets/template/angle_person_event_left/bg_black.png

.../src/assets/template/angle_person_event_left/bg_white.png

...src/assets/template/angle_person_event_right/bg_black.png

...src/assets/template/angle_person_event_right/bg_white.png

frontend/src/assets/template/base_person_event/bg_black.png

frontend/src/assets/template/base_person_event/bg_white.png

frontend/src/assets/template/right_person_event/bg_black.png

frontend/src/assets/template/right_person_event/bg_white.png

frontend/src/templates.js

frontend/src/utils.js

...rc/views/angle_person_event_left/AnglePersonEventLeft.vue

frontend/src/views/angle_person_event_left/canvas.js

.../views/angle_person_event_right/AnglePersonEventRight.vue

frontend/src/views/angle_person_event_right/canvas.js

frontend/src/views/avatar/Avatar.vue

frontend/src/views/base_person_event/BasePersonEvent.vue