Planetoid-DB 0.9.18.81

What's Changed

• Updated image link in README.md by @mjohne in #845
• Updated CHANGELOG for version 0.9.17.80 by @mjohne in #846
• Refactor: Extract shared helpers, split PlanetoidDBForm, deduplicate exporter code by @mjohne with @Copilot in #852
• Updated documentation comments by @mjohne in #854
• Moved database methods to PlanetoidDBForm.DatabaseUpdates.cs by @mjohne in #855
• Moved decoder methods to PlanetoidDBForm.Decoders.cs by @mjohne in #856
• Added export support for Typst files by @mjohne in #857
• Updated to version 0.9.18.81 by @mjohne in #858

Full Changelog: 0.9.17.80.843.2844...0.9.18.81.858.2891