fix(news): show header only on post list + fix style

.../post/components/post-details/post-details.component.html

src/app/post/components/post-list/post-list.component.html

src/app/post/components/post-list/post-list.component.scss

.../post/components/post-publish/post-publish.component.html

.../post/components/post-publish/post-publish.component.scss

src/app/post/news.component.html

src/assets/scss/_ghost.scss