Update README.md

Author: jaeyunn15

README.md

@@ -1,7 +1,10 @@
+# 🚧🚧🚧🚧 Work In Progress 🚧🚧🚧🚧
+
 # Thunder
 
 A WebSocket library that draws heavily from the [Scarlet](https://github.com/Tinder/Scarlet) by Tinder.     
-Currently, support only for Coroutine Flow. 
+The overall design of this library is very similar to Scarlet.     
+Currently, support only for Coroutine Flow.     
 
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 ## Download First
@@ -28,6 +31,13 @@ dependencies {
 }
 ~~~
 
+---
+## Restriction 🚨
+We need to target **Java 17** because the library is aligned with **Java 17**.      
+In the future, we will respond by lowering the Java version.
+
+
+
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 ## Usage