refactor(repo-card): use iife and async loading

layouts/shortcodes/github.html

@@ -68,6 +68,7 @@
       {{ $fetchRepo := resources.Get "js/fetch-repo.js" }}
       {{ $fetchRepo = $fetchRepo | resources.Minify | resources.Fingerprint ($.Site.Params.fingerprintAlgorithm | default "sha512") }}
       <script
+        async
         type="text/javascript"
         src="{{ $fetchRepo.RelPermalink }}"
         integrity="{{ $fetchRepo.Data.Integrity }}"