vweb: enable @ logic in the header + fix the example

examples/vweb/vweb_example.v

@@ -31,7 +31,7 @@ pub fn (app mut App) index() {
 	$vweb.html()
 }
 
-pub fn (app & App) text() {
+pub fn (app mut App) text() {
 	app.vweb.text('Hello world')
 }
 

vlib/vweb/tmpl/tmpl.v

@@ -15,7 +15,7 @@ const (
 
 pub fn compile_template(path string) string {
 	//lines := os.read_lines(path)
-	html := os.read_file(path) or {
+	mut html := os.read_file(path) or {
 		panic('html failed')
 	}
 	mut	header := ''
@@ -24,13 +24,14 @@ pub fn compile_template(path string) string {
 			panic('html failed')
 		}
 		header = h.replace('\'', '"')
+		html = header + html
 	}
 	lines := html.split_into_lines()
 	mut s := strings.new_builder(1000)
 	//base := path.all_after('/').replace('.html', '')
 	s.writeln('
 mut sb := strings.new_builder(${lines.len * 30})
-header := \'$header\'
+header := \' \' // TODO remove
 _ = header
 //footer := \'footer\'
 ')