Project: angular
Task (moderate): 1) Add 'Edit' appealing blue button (.edit-btn) in top&right of blog.component.ts. When clicked, toggle blog-form to edit the content of selected Blog. The Title of blog-form is 'Edit Form' in this case. When submitted, update selected Blog. 2) The logic of Edit is appended to a service blog.service.ts; 3) Constraint: blog-form should be singleton, ONLY ONE instance of blog-form exists.