Issue #3508441 by pdureau: Update components to UI Patterns 2

Closes #3508441

components/article/article.component.yml

+name: Article
+description: "A long-form body of text. This is typically multiple paragraphs, often with subheadings, and should be the primary content on the page."
+links:
+  - https://protocol.mozilla.org/components/detail/article.html
+slots:
+  title:
+    title: Title
+    description: "Article title. Plain text."
+  content:
+    title: Content
+    description: "Article content"
+props:
+  type: object
+  properties:
+    heading_level:
+      title: "Heading level"
+      type: integer
+      enum:
+        - 1
+        - 2
+        - 3
+        - 4
+        - 5
+        - 6
+      "meta:enum":
+        1: "h1 (Default)"
+        2: h2
+        3: h3
+        4: h4
+        5: h5
+        6: h6