Add a 'ParseTemplate' method on view engines to manually parse and add a template from a text

examples at: https://github.com/kataras/iris/tree/master/_examples/view/parse-template

relative to: https://github.com/kataras/iris/issues/1617

_examples/view/parse-template/jet/main.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"reflect"
+
+	"github.com/kataras/iris/v12"
+	"github.com/kataras/iris/v12/view"
+)
+
+func main() {
+	e := iris.Jet(nil, ".jet") // You can still use a file system though.
+	e.AddFunc("greet", func(args view.JetArguments) reflect.Value {
+		msg := "Hello, " + args.Get(0).String() + "!"
+		return reflect.ValueOf(msg)
+	})
+	err := e.ParseTemplate("program.jet", `<h1>{{greet(.Name)}}</h1>`)
+	if err != nil {
+		panic(err)
+	}
+
+	app := iris.New()
+	app.RegisterView(e)
+	app.Get("/", index)
+
+	app.Listen(":8080")
+}
+
+func index(ctx iris.Context) {
+	ctx.View("program.jet", iris.Map{
+		"Name": "Gerasimos",
+	})
+}