Support deno 1.3.x/0.67.0; replace handlebars with view_engine library

lib/src/const/view_engines.ts

@@ -0,0 +1,20 @@
+
+export enum ViewEngine {
+    Denjuck = 'Denjuck',
+    Ejs = 'Ejs',
+    Handlebars = 'Handlebars',
+}
+
+export enum ViewFileExtension {
+    Denjuck = '.html',
+    Ejs = '.ejs',
+    Handlebars = '.hbs',
+}
+
+export function isViewEngine(what: any): what is ViewEngine {
+    return (['Denjuck', 'Ejs', 'Handlebars'].includes(String(what)))
+}
+
+export function isViewFileExtension(what: any): what is ViewFileExtension {
+    return (['.html', '.ejs', '.hbs']).includes(String(what))
+}