Add discovery documentation

Signed-off-by: Marcus Crane <marcus.crane@lightspeedhq.com>

docs/integrations/github/discovery.md

@@ -80,6 +80,21 @@ catalog:
         filters: # optional filters
           branch: 'develop' # optional string
           repository: '.*' # optional Regex
+      topicProviderId:
+        organization: 'backstage' # string
+        catalogPath: '/catalog-info.yaml' # string
+        filters:
+          branch: 'main' # string
+          repository: '.*' # Regex
+          topic: 'backstage-exclude' # optional string
+      topicProviderInclusionId:
+        organization: 'backstage' # string
+        catalogPath: '/catalog-info.yaml' # string
+        filters:
+          branch: 'main' # string
+          repository: '.*' # Regex
+          topic: 'backstage-include' # optional string
+          topicIncludesIfMatch: true # optional boolean (default: false)
 ```
 
 This provider supports multiple organizations via unique provider IDs.
@@ -96,6 +111,12 @@ This provider supports multiple organizations via unique provider IDs.
     String used to filter results based on the branch name.
   - **repository** _(optional)_:
     Regular expression used to filter results based on the repository name.
+  - **topic** _(optional)_:
+    String used to filter results based on repository topics. By default, repositories that match the topic filter will be **ignored**. See below for the inverse.
+    This is useful for excluding excess locations from being registered such as hackathon experiments, practical tests, non-production tooling and so on.
+  - **topicIncludesIfMatch** _(optional)_:
+    Default: `false`
+    If set to `true` and a topic filter is set, **ONLY** repositories matching the topic filter will have a location registered.
 - **organization**:
   Name of your organization account/workspace.
   If you want to add multiple organizations, you need to add one provider config each.