Issue #3489054: Make the "add to cart" threshold configurable

config/install/project_browser.admin_settings.yml

config/schema/project_browser.schema.yml

src/Element/ProjectBrowser.php

sveltejs/css/claro.css

sveltejs/public/build/bundle.js

sveltejs/public/build/bundle.js.map

sveltejs/src/ProcessQueueButton.svelte

sveltejs/src/Project/ActionButton.svelte

sveltejs/src/ProjectBrowser.svelte

sveltejs/src/QueueProcessor.js

sveltejs/src/constants.js

...les/project_browser_test/project_browser_test.routing.yml

...roject_browser_test/src/Controller/TestPageController.php

tests/src/Functional/InstallerControllerTest.php

...rc/FunctionalJavascript/ProjectBrowserInstallerUiTest.php

tests/src/Kernel/CoreNotUpdatedValidatorTest.php

tests/src/Kernel/DatabaseTablesTest.php

tests/src/Kernel/PackageNotInstalledValidatorTest.php