update samples readme to include docs and remove broken links

samples/readme.md

@@ -3,12 +3,10 @@ A set of helpful samples for the [Java Sendbird Platform SDK](https://github.com
 Includes examples of moderation, announcements, auto messages and a number of others.
 
 # Samples
-Samples included in this repo
- - Creating a user session token
- - Pushing out a targeted announcement 
- - Configuring a channels automatic messages
- - Counting a users unread messages in a specific channel
- - Creating, updating and deleting a user.
- - Freezing a channel
+Samples included in this repo:
 
-[See the code here](src/main/java/Samples.java)
+ - Creating a user session token  - [docs](https://sendbird.com/docs/chat/v3/platform-api/user/managing-session-tokens/issue-a-session-token◊)
+ - Pushing out a targeted announcement - [docs](https://sendbird.com/docs/chat/v3/platform-api/message/announcements/create-an-announcement) 
+ - Counting a users unread messages in a specific channel - [docs](https://sendbird.com/docs/chat/v3/platform-api/message/read-receipts/get-number-of-unread-messages-per-member#2-response)
+ - Creating, updating and deleting a user - [docs](https://sendbird.com/docs/chat/v3/platform-api/user/creating-users/create-a-user)
+ - Freezing a channel - [docs](https://sendbird.com/docs/chat/v3/platform-api/moderation/freezing-a-channel/freeze-a-group-channel)