feat(types): Add TypeScript typings for ssr (#673)

ssr/index.d.ts

@@ -0,0 +1,21 @@
+import {ApolloProvider} from "vue-apollo";
+
+interface GetStatesOptions {
+    exportNamespace?: string;
+}
+
+interface ExportStatesOptions {
+    globalName?: string;
+    attachTo?: string;
+    useUnsafeSerializer?: boolean;
+}
+
+interface ApolloSsr {
+    serializeStates(provider: ApolloProvider, options?: GetStatesOptions): string
+    getStates(provider: ApolloProvider, options?: GetStatesOptions): {[key: string]: {}}
+    exportStates(provider: ApolloProvider, options: ExportStatesOptions): string
+}
+
+declare const ssr: ApolloSsr
+
+export default ssr;