Added inline editing/delete to posts

Did quick work of inline edit/del for posts, tahnks to existing code from edit/del of comments. To make the visual transition less jumpy/jarring when switching to edit mode (a textarea appears over the body text of the post), I set the textarea style height to reflect the scroll height of the text content in the textarea on click of the 'edit' btn.

editPostTextarea.style.height = 'auto'
editPostTextarea.style.height = `${editPostTextarea.scrollHeight}px`

Also added auto resize so that the textarea will extend vertically automagically as you type.

Also added `this.$root.$emit('fetchPosts')` upon delete so that the main feed on the home page will reload to reflect the absence of the deleted post

Tech debt: Edit or delete of post title, tagged goals not available yet. No auto edit/delete of related comments and notifs this time. I think I can let it pass till next round.