docs(guide/Components): clarify output events with extra example and note
docs(guide/Components): clarify output events with extra example and note

Add additional line from example which demonstrates using the snake cased attribute binding in
parent component template.
Add note clarifying camelCase to snake-case requirement to use the Output binding callback feature.

Closes #14365

Real-Currents/angular.js,Real-Currents/angular.js,Real-Currents/angular.js,Real-Currents/angular.js