add desc and examples for inline variable action

docs/user/features.md

@@ -270,6 +270,21 @@ fn foo() {
 }
 ```
 
+- Inline local variable:
+
+```rust
+// before:
+fn foo() {
+    let a<|> = 1 + 1;
+    let b = a * 10;
+}
+
+// after:
+fn foo() {
+    let b = (1 + 1) * 10;
+}
+```
+
 -- Remove `dbg!`
 
 ```rust