Switch away from Nunjucks to another templating language

[uncenter]

Better support for IDE tooling/autocomplete, formatting, more maintained, etc.

Liquid

New tooling, smaller ecosystem, okay editor support. Separate formatter required.

• https://aesthetic.js.org/introduction/language-support/#support-list
• https://github.com/panoply/liquify
• https://github.com/harttle/liquidjs

TSX

TypeScript, intellisense/great editor support, fully supported by Biome. Front matter not supported though.

• https://www.jetbrains.com/guide/javascript/tutorials/eleventy-tsx/tsx-templates/
• https://www.11ty.dev/docs/languages/typescript/

Vento/Squirrelly

Lack of tooling, not supported by Biome, Squirrely barely maintained.