Option to adjust date format

[tomson]

### Option to format the date of a post
- [ ] https://github.com/TryGhost/Source/blob/main/post.hbs

[tomson]

Change <time class="gh-article-meta-date" datetime="{{date format="YYYY-MM-DD"}}">{{date}}</time> to <time class="gh-article-meta-date" datetime="{{date format="D MMM YYYY"}}">{{date format="D MMM YYYY"}}</time> to allow customisation of local date format.