feat(outputs): app-slug and installation-id (#105)

It is convenient to use `https://api.github.com/users/$app_slug[bot]` to
obtain the corresponding account ID later.
Then build `Signed-off-by: $app_slug[bot]
<$id+$app_slug[bot]@users.noreply.github.com>`.

Currently, there is no Linux environment to build test snapshot files

tests/main-token-get-owner-set-to-user-fail-response.test.js

@@ -5,8 +5,9 @@ await test((mockPool) => {
   process.env.INPUT_OWNER = "smockle";
   delete process.env.INPUT_REPOSITORIES;
 
-  // Mock installation id request
+  // Mock installation ID and app slug request
   const mockInstallationId = "123456";
+  const mockAppSlug = "github-actions";
   mockPool
     .intercept({
       path: `/orgs/${process.env.INPUT_OWNER}/installation`,
@@ -30,7 +31,7 @@ await test((mockPool) => {
     })
     .reply(
       200,
-      { id: mockInstallationId },
+      { id: mockInstallationId, "app_slug": mockAppSlug },
       { headers: { "content-type": "application/json" } }
     );
 });