Include example of catalog.ts update for discovery interval change.

Signed-off-by: Kyle Smith <kyle.smith@salsify.com>

docs/integrations/github/discovery.md

@@ -38,17 +38,28 @@ The target is composed of three parts:
 
 ## GitHub API Rate Limits
 
-GitHub
-[rate limits](https://docs.github.com/en/rest/overview/resources-in-the-rest-api#rate-limiting)
-API requests to 5,000 per hour (or more for Enterprise accounts). The default
-Backstage catalog backend refreshes data every 100 seconds, which issues an API
-request for each discovered location.
+GitHub [rate limits] API requests to 5,000 per hour (or more for Enterprise
+accounts). The default Backstage catalog backend refreshes data every 100
+seconds, which issues an API request for each discovered location.
 
 This means if you have more than ~140 catalog entities, you may get throttled by
 rate limiting. This will soon be resolved once catalog refreshes make use of
 ETags; to work around this in the meantime, you can change the refresh rate of
-the catalog in your `packages/backend/src/plugins/catalog.ts` file, or configure
-Backstage to use the [github-apps plugin](../../plugins/github-apps.md).
+the catalog in your `packages/backend/src/plugins/catalog.ts` file:
+
+```typescript
+const builder = await CatalogBuilder.create(env);
+
+// For example, to refresh every 5 minutes (300 seconds).
+builder.setRefreshIntervalSeconds(300);
+```
+
+Alternatively, or additionally, you can use the [github-apps plugin] which
+carries a much higher rate limit at GitHub.
 
 This is true for any method of adding GitHub entities to the catalog, but
 especially easy to hit with automatic discovery.
+
+[rate limits]:
+  https://docs.github.com/en/rest/overview/resources-in-the-rest-api#rate-limiting
+[github-apps plugin]: ../../plugins/github-apps.md