add minijinja templating example

templating/minijinja/README.md

@@ -0,0 +1,13 @@
+# MiniJinja
+
+Minimal example of using the template engine [MiniJinja](https://github.com/Keats/tera) that displays a form.
+
+## Usage
+
+```sh
+cd templating/minijinja
+cargo run
+```
+
+- <http://localhost:8080>
+- <http://localhost:8080/non-existing-page> - 404 page rendered using template