support alternative file formats for content, besides '.lr' (was: support Markdown with YAML Front Matter)

There is a common, widely used data format for static site generators known as “Markdown with YAML Front Matter”. The contents.lr format is almost the same, with some key differences. If Lektor supported Markdown with YAML Front Matter, then all sorts of other tools like editors, syntax highlighters, translation tools, etc will automatically support the Lektor files. They could be called contents.md, for example.

This is a file from a Lektor site:

section: localization
---
section_id: localization
---
color: primary
---
_template: layout.html
---
title: Localization
---
subtitle: We want Tor to work for everyone in the world, which means our software must be translated into a lot of languages.
---
cta: Help us translate
---
key: 4
---
html: localization.html
---
body:

##Localization is how we reach a global community.

In order for Tor to work for everyone, it needs to speak everyone's languages.
Our volunteer translation team works hard to make this a reality, and we can always use more help.
Our current translation priorities are translating [Tor Browser](https://torpat.ch/locales), Tor Browser documentation, and the [Tor Project website](https://torpat.ch/tpo-locales), but there are many other documents that we could use help translating as well.

In Markdown with YAML Front Matter, it would look like this:

---
section: localization
section_id: localization
color: primary
_template: layout.html
title: Localization
subtitle: We want Tor to work for everyone in the world, which means our software must be translated into a lot of languages.
cta: Help us translate
key: 4
html: localization.html
---

##Localization is how we reach a global community.

In order for Tor to work for everyone, it needs to speak everyone's languages.
Our volunteer translation team works hard to make this a reality, and we can always use more help.
Our current translation priorities are translating [Tor Browser](https://torpat.ch/locales), Tor Browser documentation, and the [Tor Project website](https://torpat.ch/tpo-locales), but there are many other documents that we could use help translating as well.

Here are some docs on the format:

• https://jekyllrb.com/docs/front-matter/
• https://gohugo.io/content-management/front-matter/
• https://assemble.io/docs/YAML-front-matter.html
• https://www.gatsbyjs.org/docs/adding-markdown-pages/#frontmatter-for-metadata-in-markdown-files

And here are many libraries which support this format:

• Python: https://github.com/eyeseast/python-frontmatter
• Python: https://github.com/jonbeebe/frontmatter
• Javascript: https://github.com/jxson/front-matter
• Javascript: https://github.com/dworthen/js-yaml-front-matter
• Ruby: https://github.com/jonschlinkert/gray-matter

@uniqx

[nixjdm]

move us away from the file format holy wars

Amen.

Seriously though, having a standardized entry point seems like a good refactor to me, and it might be inroads into implementing #477 and ingesting bulk content.

It’s also worth repeating I think that people can set their IDEs to a Markdown mode and immediately get syntax highlighting for their markdown fields in a .lr file. I’d bet that’s really the driver for a lot of people reading this. Go ahead and do this now if you’re one of those people. 🙂

[xlotlu]

Seriously though, having a standardized entry point seems like a good refactor to me, and it might be inroads into implementing #477 and ingesting bulk content.

@nixjdm I think I want to give this a crack. If you have some pointers, they’re welcome.

It’s also worth repeating I think that people can set their IDEs to a Markdown mode and immediately get syntax highlighting for their markdown fields in a .lr file.

The point of editing them has also come up (#745). Tools that deal with md+fm obviously mess the lr up.