Added method to join group (#417)

* Added method to join group

* Added method to join group in README

README.md

@@ -527,6 +527,12 @@ Of course, replace ``` xyz ``` with an actual ID.
     // Or if you've left the group -- call this
     const metadata2 = await conn.groupMetadataMinimal ("abcd-xyz@g.us") 
     ```
+- To join the group using the invitation code
+    ``` ts
+    const response = await conn.acceptInvite ("xxx")
+    console.log("joined to: " + response.gid)
+    ```
+Of course, replace ``` xxx ``` with invitation code.
 
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src/Tests/Tests.Groups.ts

@@ -20,6 +20,11 @@ WAConnectionTest('Groups', (conn) => {
         assert.ok(code)
         assert.strictEqual(typeof code, 'string')
     })
+    it('should joined group via invite code', async () => {
+        const response = await conn.acceptInvite(gid)
+        assert.ok(response.status)
+        assert.strictEqual(response.status, response.gid)
+    })
     it('should retrieve group metadata', async () => {
         const metadata = await conn.groupMetadata(gid)
         assert.strictEqual(metadata.id, gid)

src/WAConnection/8.Groups.ts

@@ -177,4 +177,9 @@ export class WAConnection extends Base {
         const response = await this.query({json, expect200: true, requiresPhoneConnection: false})
         return response.code as string
     }
-}
+    /** Join group via invite code */
+    async acceptInvite(jid) {
+        const response = await this.query({ json: ['action', 'invite', jid], expect200: true })
+        return response
+    }
+}