Add id to release block

This commit adds an id attribute to release blocks to allow them to be
targeted as anchor links.

app/assets/javascripts/releases/components/release_block.vue

@@ -53,7 +53,7 @@ export default {
 };
 </script>
 <template>
-  <div class="card">
+  <div :id="release.tag_name" class="card">
     <div class="card-body">
       <h2 class="card-title mt-0">
         {{ release.name }}

spec/javascripts/releases/components/release_block_spec.js

@@ -88,6 +88,10 @@ describe('Release block', () => {
     vm.$destroy();
   });
 
+  it("renders the block with an id equal to the release's tag name", () => {
+    expect(vm.$el.id).toBe('18.04');
+  });
+
   it('renders release name', () => {
     expect(vm.$el.textContent).toContain(release.name);
   });