add the Context's helpers when working with subdomains

Routing-subdomains.md

@@ -87,3 +87,31 @@ app.SubdomainRedirect(app, www)
 ```
 
 The above will redirect all http(s)://mydomain.com/%anypath% to http(s)://www.mydomain.com/%anypath%.
+
+The `Context` offers four main methods when working with subdomains that may be helpful for you.
+
+```go
+// Host returns the host part of the current url.
+Host() string
+// Subdomain returns the subdomain of this request, if any.
+// Note that this is a fast method which does not cover all cases.
+Subdomain() (subdomain string)
+// IsWWW returns true if the current subdomain (if any) is www.
+IsWWW() bool
+// FullRqeuestURI returns the full URI,
+// including the scheme, the host and the relative requested path/resource.
+FullRequestURI() string
+```
+
+**Usage**
+
+```go
+func info(ctx iris.Context) {
+    method := ctx.Method()
+    subdomain := ctx.Subdomain()
+    path := ctx.Path()
+
+    ctx.Writef("\nInfo\n\n")
+    ctx.Writef("Method: %s\nSubdomain: %s\nPath: %s", method, subdomain, path)
+}
+```