examples: replace all app.Run(iris.Addr(...)) with app.Listen just for the shake of simplicity, both are doing the same exact thing as it's described on the http listening first example.

Former-commit-id: d20afb2e899aee658a8e0ed1693357798df93462

_examples/file-server/single-page-application/basic/main.go

@@ -32,5 +32,5 @@ func main() {
 	// http://localhost:8080/index.html
 	// http://localhost:8080/app.js
 	// http://localhost:8080/css/main.css
-	app.Run(iris.Addr(":8080"))
+	app.Listen(":8080")
 }

_examples/file-server/single-page-application/embedded-single-page-application-with-other-routes/main.go

@@ -61,5 +61,5 @@ func main() {
 	// http://localhost:8080/.well-known/metrics
 	//
 	// Remember: we could use the root wildcard `app.Get("/{param:path}")` and serve the files manually as well.
-	app.Run(iris.Addr(":8080"))
+	app.Listen(":8080")
 }

_examples/file-server/single-page-application/embedded-single-page-application/main.go

@@ -37,5 +37,5 @@ func main() {
 	// http://localhost:8080/app.js
 	// http://localhost:8080/css/main.css
 	// http://localhost:8080/app2
-	app.Run(iris.Addr(":8080"))
+	app.Listen(":8080")
 }