Merge branch '3398525-add-an-api' into '11.x'

core/core.services.yml

core/lib/Drupal/Core/Asset/ImportMapsManager.php

core/lib/Drupal/Core/Asset/ImportMapsManagerInterface.php

core/lib/Drupal/Core/Render/theme.api.php

core/misc/cspell/dictionary.txt

core/modules/system/system.module

...ts/modules/importmaps_test/importmaps_test.importmaps.yml

...em/tests/modules/importmaps_test/importmaps_test.info.yml

...sts/modules/importmaps_test/importmaps_test.libraries.yml

...stem/tests/modules/importmaps_test/importmaps_test.module

...tests/modules/importmaps_test/importmaps_test.routing.yml

...les/system/tests/modules/importmaps_test/js/bar-scoped.js

core/modules/system/tests/modules/importmaps_test/js/bar.js

core/modules/system/tests/modules/importmaps_test/js/foo.js

...ules/system/tests/modules/importmaps_test/js/scope/foo.js

...stem/tests/modules/importmaps_test/src/TestController.php

..._imports_only/importmaps_test_imports_only.importmaps.yml

...s_test_imports_only/importmaps_test_imports_only.info.yml

...st_scopes_only/importmaps_test_scopes_only.importmaps.yml

...aps_test_scopes_only/importmaps_test_scopes_only.info.yml