Merge pull request #35656 from fivenp/docs/add-design-contribution-guidelines

docs: add design contribution guidelines

DESIGN.md

+# Nextcloud Design contribution guidelines
+
+## 👋 Welcome
+
+At Nextcloud we want to make sure to have everything in place to enable designers to contribute – making our apps universally accessible and easy to use.
+
+## 🚢 How to contribute design
+
+We have a dedicated page with more in-detail guidelines on our website: 
+https://nextcloud.com/design/
+
+**TL;DR**
+
+1. Check out open [issues](https://github.com/nextcloud/server/issues) here on GitHub (we label them with `design`)
+2. Make sure create publicly accessible assets 
+3. Add your contributions to an issue and we promise we will review your contribution carefully and foster discussions
+
+[This issue](https://github.com/nextcloud/desktop/issues/877) has examples of other apps, some simple mockups, and specifications about the design. In the discussions in the comments there are updates to the design as well.
+
+[This pull request](https://github.com/nextcloud/desktop/pull/1565) by a developer has the implementation of that issue, the changes they made, and more design discussions and adjustments.
+
+**We encourage you to:**
+
+- Get in touch with the team by joining our [public Talk channel](https://cloud.nextcloud.com/call/gqff69i8)

README.md

@@ -2,6 +2,7 @@
 [![Scrutinizer Code Quality](https://scrutinizer-ci.com/g/nextcloud/server/badges/quality-score.png?b=master)](https://scrutinizer-ci.com/g/nextcloud/server/?branch=master)
 [![codecov](https://codecov.io/gh/nextcloud/server/branch/master/graph/badge.svg)](https://codecov.io/gh/nextcloud/server)
 [![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/209/badge)](https://bestpractices.coreinfrastructure.org/projects/209)
+[![Design](https://contribute.design/api/shield/nextcloud/server)](https://contribute.design/nextcloud/server)
 
 **A safe home for all your data.**