:sparkles: adding embed rules for single block

vue-theme/src/components/content-block/block.vue

 .block.gallery(v-if="block.hasOwnProperty('gallery')")
     p place-holder gallery {{ block.gallery }}
 
+.block.embed(v-else-if="block[0].blockName == 'core/embed'")
+    .youtube(v-if="block[0].attrs.providerNameSlug == 'youtube'")
+        p youtube: {{ block[0].attrs }}
+    .not-youtube(v-else)
+        p not youtube: {{ block[0].attrs }}
 rblock(v-else-if="typeof block === 'object'" :block="block")
         
 .block.single(v-else)

vue-theme/src/pages/single.vue

 <style lang="postcss">
 .page--single
     article
-        ul
+        > ul
             list-style: none
             li
                 img