Updating README usage version to 0.20

BigBallard · zonyitoo · commit 700a8bf1134c · 2024-03-11T11:10:09.000+08:00
diff --git a/README.md b/README.md
@@ -10,7 +10,7 @@ This is an INI file parser in [Rust](http://www.rust-lang.org/).
 
 ```toml
 [dependencies]
-rust-ini = "0.19"
+rust-ini = "0.20"
 ```
 
 ## Usage
