Update the middleware documentation

docs/content/middlewares/stripprefix.md

@@ -1,13 +1,66 @@
-# TODO -- StripPrefix
+# StripPrefix
 
 Removing Prefixes From the Path Before Forwarding the Request
 {: .subtitle }
 
-## OldContent
- 
-Use a `*Strip` matcher if your backend listens on the root path (`/`) but should be routeable on a specific prefix.
-For instance, `PathPrefixStrip: /products` would match `/products` but also `/products/shoes` and `/products/shirts`.  
-Since the path is stripped prior to forwarding, your backend is expected to listen on `/`.  
+`TODO: add schema`
+
+Remove the specified prefixes from the URL path.
+
+## Configuration Examples
+
+```yaml tab="Docker"
+# Replace the path by /foo
+labels:
+- "traefik.http.middlewares.test-stripprefix.stripprefix.prefixes=foobar, fiibar"
+```
+
+```yaml tab="Kubernetes"
+# Replace the path by /foo
+apiVersion: traefik.containo.us/v1alpha1
+kind: Middleware
+metadata:
+  name: test-stripprefix
+spec:
+  StripPrefix:
+    prefixes: "foobar, fiibar"
+```
+
+```yaml tab="Rancher"
+# Replace the path by /foo
+labels:
+- "traefik.http.middlewares.test-stripprefix.stripprefix.prefixes=foobar, fiibar"
+```
+
+```toml tab="File"
+# Replace the path by /foo
+[http.middlewares]
+  [http.middlewares.test-stripprefix.StripPrefix]
+     prefixes: "foobar, fiibar"
+```
+
+## Configuration Options
+
+### General
+
+The StripPrefix middleware will:
+
+- strip the matching path prefix.
+- store the matching path prefix in a `X-Forwarded-Prefix` header.
+
+!!! tip
+    
+    Use a `StripPrefix` middleware if your backend listens on the root path (`/`) but should be routeable on a specific prefix.
+
+### `prefixes`
+
+The `prefixes` option defines the prefixes to strip from the request URL.
+
+For instance, `/products` would match `/products` but also `/products/shoes` and `/products/shirts`.
+
+Since the path is stripped prior to forwarding, your backend is expected to listen on `/`.
+
 If your backend is serving assets (e.g., images or Javascript files), chances are it must return properly constructed relative URLs.  
 Continuing on the example, the backend should return `/products/shoes/image.png` (and not `/images.png` which Traefik would likely not be able to associate with the same backend).  
-The `X-Forwarded-Prefix` header (available since Traefik 1.3) can be queried to build such URLs dynamically.
+
+The `X-Forwarded-Prefix` header can be queried to build such URLs dynamically.