Release 0.4

What's Changed

• Updates for Lektor 3.4 & mistune 2 by @dairiki in #15
• Move project metadata to pyproject.toml & add coverage tests by @dairiki in #18
• Further fixes to support mistune2 (Lektor 3.4) by @dairiki in #17
• Prepare to release 0.4 by @dairiki in #19

New Contributors

• @dairiki made their first contribution in #15

Full Changelog: 0.3.1...v0.4.0