feat: add schema.org json-ld objects to podcasts, episodes, posts and comments pages

- refactor meta-tags by generating them in the controller and injecting them into the views
- use
`melbahja/seo` library to build opengraph and twitter meta-tags + schema.org objects

app/Controllers/HomeController.php

@@ -36,6 +36,7 @@ class HomeController extends BaseController
 
         // default behavior: list all podcasts on home page
         $data = [
+            'metatags' => get_home_metatags(),
             'podcasts' => $allPodcasts,
         ];