Add LSIF to README

Author: chrismwendt

README.md

@@ -280,6 +280,14 @@ $ docker exec -ti lang-go sh
 Cloning into 'your-private-repo'...
 ```
 
+## LSIF
+
+LSIF support can be enabled by setting:
+
+```json
+  "codeIntel.lsif": true
+```
+
 ## Scaling out by increasing the replica count
 
 You can run multiple instances of the go-langserver and distribute connections between them in Kubernetes by setting `spec.replicas` in the deployment YAML: