add a ParseTemplate to the HTML view engine.

relative to: #1617

Wait for an answer from the issuer and if that's the expected behavior, do the same for the rest of the view engines

_examples/view/parse-template/main.go

@@ -0,0 +1,35 @@
+// Package main shows how to parse a template through custom byte slice content.
+package main
+
+import "github.com/kataras/iris/v12"
+
+func main() {
+	app := iris.New()
+	// To not load any templates from files or embedded data,
+	// pass nil or empty string on the first argument:
+	// view := iris.HTML(nil, ".html")
+
+	view := iris.HTML("./views", ".html")
+	view.ParseTemplate("program.html", []byte(`<h1>{{greet .Name}}</h1>`), iris.Map{
+		"greet": func(name string) string {
+			return "Hello, " + name + "!"
+		},
+	})
+
+	app.RegisterView(view)
+	app.Get("/", index)
+	app.Get("/layout", layout)
+
+	app.Listen(":8080")
+}
+
+func index(ctx iris.Context) {
+	ctx.View("program.html", iris.Map{
+		"Name": "Gerasimos",
+	})
+}
+
+func layout(ctx iris.Context) {
+	ctx.ViewLayout("layouts/main.html")
+	index(ctx)
+}