* Create astro-paper.code-snippets
* feat: allow nullable modDatetime
this is needed to allow the snippet to work with a blank date time, and is a precursor of adding in a modified date time setting hook
* Update astro-paper.code-snippets to make feat false by default
* feat: add modified datetime in blog posts
Add modDatetime in blogSchema. Update Datetime component to accept modDatetime. Update sorting logic. Rename datetime to pubDatetime in Datetime component.
Closes: #134
* feat: add published_time & modified_time meta tags
* docs: update related blog posts to be up-to-date
* fix: remove extra spaces in breadcrumbs