add headings

Author: kodster28

src/content/docs/style-guide/components/code.mdx

@@ -85,6 +85,8 @@ index_name = "tutorial-index"
 If you add the `playground` option to the opening code fence for a Worker example, it will
 add a "Run Worker in Playground" link that will take the user to the [Worker's playground](/workers/playground/)
 
+### Live demo
+
 ```js playground
 export default {
 	fetch() {
@@ -93,6 +95,8 @@ export default {
 };
 ```
 
+### How to use
+
 ````mdx "playground"
 ```js playground
 export default {
@@ -108,6 +112,8 @@ export default {
 If you add the `graphql-api-explorer` option to the opening code fence for a `graphql` code block, it will
 add a "Run in GraphQL API Explorer" link that will take the user to the [GraphQL API explorer](https://graphql.cloudflare.com/explorer).
 
+### Live demo
+
 ```graphql graphql-api-explorer title="A GraphQL query"
 query ASingleDatasetExample($zoneTag: string, $start: Time, $end: Time) {
 	viewer {
@@ -126,6 +132,8 @@ query ASingleDatasetExample($zoneTag: string, $start: Time, $end: Time) {
 }
 ```
 
+### How to use
+
 ````mdx "graphql-api-explorer"
 ```graphql graphql-api-explorer title="A GraphQL query"
 query ASingleDatasetExample($zoneTag: string, $start: Time, $end: Time) {