provide useSocket() function

This can be used in Vue's setup() function to inject the socket instance
where $scoket is not available:

setup() {
   const socket = useSocket()
}

Author: e-tobi

Diff for: src/plugin.js

@@ -1,5 +1,5 @@
 // eslint-disable-next-line import/no-extraneous-dependencies
-import { ref } from 'vue';
+import { ref, inject } from 'vue';
 import Observe from './Observe';
 import GlobalEmitter from './GlobalEmitter';
 import createMixin from './createMixin';
@@ -53,6 +53,8 @@ function defineSocketIoClient(socket, obj) {
   });
 }
 
+const SocketExtensionKey = Symbol('$socket');
+
 function install(app, socket, options) {
   if (!isSocketIo(socket)) {
     throw new Error('[vue-socket.io-ext] you have to pass `socket.io-client` instance to the plugin');
@@ -67,6 +69,11 @@ function install(app, socket, options) {
   app.config.optionMergeStrategies.sockets = (toVal, fromVal) => ({ ...toVal, ...fromVal });
   Observe(socket, options);
   app.mixin(createMixin(GlobalEmitter));
+  app.provide(SocketExtensionKey, $socket);
 }
 
-export { defaults, install };
+const useSocket = () => inject(SocketExtensionKey);
+
+export default {
+  defaults, install, useSocket, SocketExtensionKey,
+};

Diff for: types/index.d.ts

@@ -1,5 +1,5 @@
 // @ts-ignore
-import { PluginInstallFunction } from 'vue';
+import { InjectionKey, PluginInstallFunction } from 'vue';
 import { VueDecorator } from 'vue-class-component';
 import * as SocketIOClient from 'socket.io-client';
 // augment typings of Vue.js
@@ -23,3 +23,15 @@ declare class VueSocketIOExt {
 
 export default VueSocketIOExt;
 export const Socket: (eventName?: string) => VueDecorator;
+
+export interface SocketExtension {
+  client: SocketIOClient.Socket;
+  $subscribe: (event: string, fn: Function) => void;
+  $unsubscribe: (event: string) => void;
+  connected: boolean;
+  disconnected: boolean;
+}
+
+export declare const SocketExtensionKey: InjectionKey<SocketExtension>
+export declare const useSocket: () => SocketExtension
+