message: doc: update documentation for TransferHttpCacheModule
  Improve documentation for requests other than GET, See issue:
diff: ## TransferHttpCacheModule
  -`TransferHttpCacheModule` installs a Http interceptor that avoids duplicate `HttpClient` requests
  +`TransferHttpCacheModule` installs a Http interceptor that avoids duplicate `HttpClient` GET requests
  on the client, for requests that were already made when the application was rendered on the server
  side.
  When the module is installed in the application `NgModule`, it will intercept `HttpClient` requests
  on the server and store the response in the `TransferState` key-value store. This is transferred to the client, which then uses it to respond to the same `HttpClient` requests on the client.
  +Any requests other than GET will prevent any further requests. You may alternatively use `BrowserTransferStateModule` to write your own behaviour for caching information.
  +
  ### Usage
  To use the `TransferHttpCacheModule`, first install it as part of the top-level App module.
  