message: docs: Add TechDocs FAQ about annotation value when using external build and storage
diff: @@ -34,3 +34,14 @@ Not right now. We are currently using MkDocs to generate the documentation from
  source, so the files have to be in Markdown format. However, in the future we
  want to support other static site generators which will make it possible to use
  other file formats.
  +
  +#### What should be the value of `backstage.io/techdocs-ref` when using external build and storage?
  +
  +The value of
  +[`backstage.io/techdocs-ref`](../software-catalog/well-known-annotations.md#backstageiotechdocs-ref)
  +metadata annotation is used in the build process of TechDocs. But when
  +[`techdocs.builder`](./configuration.md) is set to `'external'` in
  +`app-config.yaml`, the value of the annotation remains unused. However the
  +annotation should still be present in entity descriptor file (e.g.
  +`catalog-info.yaml`) for Backstage to know that TechDocs is enabled for the
  +entity.
  