feat: Added Sanity documentation

markdown/dev/guides/content/sanity/en.md

@@ -0,0 +1,70 @@
+---
+title: Sanity Content Guide
+---
+
+FreeSewing uses Sanity content needs to be edited/written by non-technical contributors,
+and for images uploaded by users, such as for their profile image and so on.
+
+<Tldr>
+
+You can manage FreeSewing's Sanity content at
+[cms.freesewing.org](https://cms.freesewing.org/) 
+</Tldr>
+
+By *content that needs to be edited/written by non-technical contributors* we mean:
+
+- Newsletter posts
+- Blog posts in all languages
+- Showcase posts in all languages
+
+## Why we use Sanity
+
+The (historical) reason that we use a (headless) CMS for this lies with **the
+showcase posts**.  Our documentation is still hosted in git as MDX, and
+historically this was also the case for our blog posts and showcase posts.
+
+However, while documentation is written by contributors who are familiar with
+how we work, and blog posts are typically written by Joost, showcase posts are
+often provided by users of the site for whom submitting a pull request is a
+steep learning curve.
+
+So for this reason, we started using an external CMS to host the showcase
+posts.  And, since blog posts and showcase posts are so similar, we decided to
+use this platform for both.  Later, we added newsletter content to this list
+because this too is sometimes provided by people not so familiar with the git
+workflow.
+
+Prior to version 3, we used a self-hosted version of
+[Strapi](https://strapi.io/) for this.  And while that did what we needed,
+self-hosting adds workload to people and our backend systems, so it's not
+without its drawbacks.  Then, with the release of Strapi v4, they dropped
+support for MongoDB, which was the database we are using, so we were stuck on
+v3 of Strapi.
+
+So for FreeSewing v3 we started looking for alternatives, and after trying
+various solutions Sanity came out as the best solution for our needs.  It's a
+SaaS solution -- which is nice because it means we don't have to host anything
+-- but the flip side of the coin is that as a communal open source project, we
+obviously cannot afford it.
+
+Fortunately for us, the same reasons that mean we don't have any money also
+mean that Sanity took pity on us, and they agreed to waive their fees and let
+us use their service free of charge.  So, Sanity is now a FreeSewing sponsor,
+and since everything is in place already, we also use them to host user images
+because honestly it's a really nice service.
+
+## How to manage Sanity content
+
+As Sanity is a headless CMS, you essentially have to talk to the API to manage
+your content.
+ 
+Fear not though, we don't expect you to do that. The Sanity Studio is a
+web-based frontend that allows you to manage the content in a web environment,
+and we have an instance of it deployed at https://cms.freeseiwng.org/ that is
+pre-configured to manage FreeSewing's content.
+
+## For developers
+
+If you're looking to learn more about how to interact with the Sanity API,
+please refer to [the Sanity reference documentation](/reference/sites/sanity).
+