Added README

Author: Dimitri van Hees

README.md

@@ -0,0 +1,26 @@
+# API Guidelines
+
+This repository contains the API design guidelines for Dutch government APIs. The `components` folder contains compliant reusable OpenAPI components which can be included in OpenAPI Specifications (OAS).
+
+## Referring to components
+
+We recommend to use [jsDelivr](https://www.jsdelivr.com/network/infographic) when referring to the resuable OAS components in this repository. For example, if you want to refer to the `Content-Crs` header in `parameters.yaml`, you should use the following URL:
+
+`https://cdn.jsdelivr.net/gh/geonovum/kp-api-guidelines@1.0.0/components/parameters.yaml#/contentCrs`
+
+Example OAS syntax:
+
+```yaml
+paths:
+  /addresses:
+    get:
+      parameters:
+        - $ref: 'https://cdn.jsdelivr.net/gh/geonovum/kp-api-guidelines@1.0.0/components/parameters.yaml#/contentCrs'
+```
+
+## Versioning
+
+Please note that `1.0.0` points to the specific `1.0.0` release of the API Guidelines. Version ranges are also supported, but not recommended:
+
+- `/kp-api-guidelines@1.0/`: latest patch release in the `1.0.x` range, e.g. `1.0.3`
+- `/kp-api-guidelines@1/`: latest minor release in the `1.x.x` range, e.g. `1.2.1`.