Fix tsdoc and update reference docs (#4744)

* fix tsdoc

* fix tsdoc in rc

* update reference docs

Author: Feiyang1

common/api-review/firestore-exp.api.md

@@ -200,7 +200,7 @@ export function getDocsFromCache<T>(query: Query<T>): Promise<QuerySnapshot<T>>;
 export function getDocsFromServer<T>(query: Query<T>): Promise<QuerySnapshot<T>>;
 
 // @public
-export function getFirestore(app: FirebaseApp): FirebaseFirestore;
+export function getFirestore(app?: FirebaseApp): FirebaseFirestore;
 
 // @public
 export function increment(n: number): FieldValue;

common/api-review/firestore-lite.api.md

@@ -158,7 +158,7 @@ export function getDoc<T>(reference: DocumentReference<T>): Promise<DocumentSnap
 export function getDocs<T>(query: Query<T>): Promise<QuerySnapshot<T>>;
 
 // @public
-export function getFirestore(app: FirebaseApp): FirebaseFirestore;
+export function getFirestore(app?: FirebaseApp): FirebaseFirestore;
 
 // @public
 export function increment(n: number): FieldValue;

common/api-review/installations-exp.api.md

@@ -23,7 +23,7 @@ export interface _FirebaseInstallationsInternal {
 export function getId(installations: FirebaseInstallations): Promise<string>;
 
 // @public
-export function getInstallations(app: FirebaseApp): FirebaseInstallations;
+export function getInstallations(app?: FirebaseApp): FirebaseInstallations;
 
 // @public
 export function getToken(installations: FirebaseInstallations, forceRefresh?: boolean): Promise<string>;

common/api-review/performance-exp.api.md

@@ -13,7 +13,7 @@ export interface FirebasePerformance {
 }
 
 // @public
-export function getPerformance(app: FirebaseApp): FirebasePerformance;
+export function getPerformance(app?: FirebaseApp): FirebasePerformance;
 
 // @public
 export function initializePerformance(app: FirebaseApp, settings?: PerformanceSettings): FirebasePerformance;

common/api-review/remote-config-exp.api.md

@@ -31,7 +31,7 @@ export function getBoolean(remoteConfig: RemoteConfig, key: string): boolean;
 export function getNumber(remoteConfig: RemoteConfig, key: string): number;
 
 // @public (undocumented)
-export function getRemoteConfig(app: FirebaseApp): RemoteConfig;
+export function getRemoteConfig(app?: FirebaseApp): RemoteConfig;
 
 // @public
 export function getString(remoteConfig: RemoteConfig, key: string): string;