feat(platform-server): add an API to transfer state from server (#19134)

TransferState provides a shared store that is transferred from the
server to client. To use it import BrowserTransferStateModule from the
client app module and ServerTransferStateModule from the server app
module and TransferState will be available as an Injectable object.

PR Close #19134

packages/platform-browser/src/platform-browser.ts

@@ -10,6 +10,7 @@ export {BrowserModule, platformBrowser} from './browser';
 export {Meta, MetaDefinition} from './browser/meta';
 export {Title} from './browser/title';
 export {disableDebugTools, enableDebugTools} from './browser/tools/tools';
+export {BrowserTransferStateModule, StateKey, TransferState, makeStateKey} from './browser/transfer_state';
 export {By} from './dom/debug/by';
 export {DOCUMENT} from './dom/dom_tokens';
 export {EVENT_MANAGER_PLUGINS, EventManager} from './dom/events/event_manager';