Lectern

Feature
* Serialize images ([`7cf6fd9`](https://github.com/mcbeet/lectern/commit/7cf6fd944533a4ea9210f1f795bc4839c1a793de))
* Extract image fragments ([`1c6b71b`](https://github.com/mcbeet/lectern/commit/1c6b71bd0008163226394d77b8909f7459584732))

Fix
* Use match_tokens() to check for a single code_inline ([`7117521`](https://github.com/mcbeet/lectern/commit/7117521388f5b76e0085d19301d1a9d5d5b7d86f))

Feature
* Add link fragments ([`b0d26d5`](https://github.com/mcbeet/lectern/commit/b0d26d530bd5029ea33bba8b1886a913af6ce125))

Fix
* Patch markdown_it to allow arbitrary data urls ([`bb5c05d`](https://github.com/mcbeet/lectern/commit/bb5c05df7d30e144d014fcaef36c84a802b7c51a))

Fix
* Markdown snapshots now use foldable sections ([`76359e0`](https://github.com/mcbeet/lectern/commit/76359e005ff0f833e0e3a134e78f15089a6dd3ba))

Feature
* Handle folded sections ([`9f611e5`](https://github.com/mcbeet/lectern/commit/9f611e57e766ba3e78bf7a15392fc4ab0e97650a))

Fix
* Resolve output_files relative to the context directory ([`73e4bcd`](https://github.com/mcbeet/lectern/commit/73e4bcdda5be64f5296641a9e66a048aaf35f1d5))

Documentation
* Add command-line utility help text ([`e615ba1`](https://github.com/mcbeet/lectern/commit/e615ba13b61fc0c1625c538d8290b142d16e3ea3))