feat: add readme (#791)

sdks/README.md

@@ -0,0 +1,25 @@
+# SDK
+
+## Java
+
+https://github.com/langgenius/java-client/
+
+## Go
+
+https://github.com/langgenius/dify-sdk-go
+
+## Ruby
+
+https://github.com/langgenius/ruby-sdk
+
+## Python
+
+TODO move to another place
+
+## PHP
+
+TODO move to another place
+
+## Node.js
+
+TODO move to another place