chore(docs): Add 'Prepr CMS' guide to docs

[tim-hanssen]

This PR adds the sourcing guide for Prepr (prepr.io) headless CMS.

[LekoArts]

Hi!

Thanks for the addition. Historically we let people add additional guides into our own docs for their CMSs but since a lot of new ones come out every day we switched to let people link to their own guides. Then it's not our job to keep the guide accurate.

So please use links to your own documentation and for now you can remove the plugin column since it's just the generic gatsby-source-graphql. By the way, if you want to build a more sophisticated source plugin for your CMS we recommend using https://github.com/gatsbyjs/gatsby-graphql-toolkit

CraftCMS used it for example: https://github.com/craftcms/gatsby-source-craft

[tim-hanssen]

Hi!

Thanks for the addition. Historically we let people add additional guides into our own docs for their CMSs but since a lot of new ones come out every day we switched to let people link to their own guides. Then it's not our job to keep the guide accurate.

So please use links to your own documentation and for now you can remove the plugin column since it's just the generic gatsby-source-graphql. By the way, if you want to build a more sophisticated source plugin for your CMS we recommend using https://github.com/gatsbyjs/gatsby-graphql-toolkit

CraftCMS used it for example: https://github.com/craftcms/gatsby-source-craft

Thxs @LekoArts we're actively working on a new plugin. For now I added the guide to the docs the way you suggested.

[LekoArts]

Thanks!