[TechDocs] Rebuild docs if the github source is newer than last docs build (#2353)

* Added age check for documentation in github to make sure it's up to date

* Updated failing tests

* Updated docs to explain requestUrl and storageUrl

* Updated failing tests

* Update packages/create-app/templates/default-app/app-config.yaml.hbs

* Update docs/features/techdocs/getting-started.md

Co-authored-by: Emma Indal <emmai@spotify.com>

docs/features/techdocs/getting-started.md

@@ -74,17 +74,28 @@ export { plugin as TechDocs } from '@backstage/plugin-techdocs';
 ### Setting the configuration
 
 TechDocs allows for configuration of the docs storage URL through your
-`app-config` file.
+`app-config` file. We provide two different values to be configured,
+`requestUrl` and `storageUrl`. The `requestUrl` is what the reader will request
+its data from, and `storageUrl` is where the backend can find the stored
+documentation.
 
-The default storage URL:
+The default storage and request URLs:
 
 ```yaml
 techdocs:
   storageUrl: http://localhost:7000/techdocs/static/docs
+  requestUrl: http://localhost:7000/techdocs/docs
 ```
 
-If you want to configure this to point to another storage URL, change the value
-of `storageUrl`.
+If you want `techdocs-backend` to manage building and publishing you want
+`requestUrl` to point to the default value (or wherever `techdocs-backend` is
+hosted). `storageUrl` should be where your publisher publishes your docs. Using
+the default `LocalPublish` that is the default value.
+
+If you have a setup where you are not using `techdocs-backend` for managing
+building and publishing of your documentation you want to change the
+`requestUrl` to point to your storage. In this case `storageUrl` is not
+required.
 
 ## Run Backstage locally