update readme

Author: zahash

README.md

@@ -28,12 +28,16 @@ cargo install csc
 
 ## Usage examples
 
+launch the interactive prompt by typing `csc` to run multiple computations
+
 ```sh
 a = 10
 b = a + 1.14
 c = log(b, 3) + sin(PI)
 ```
 
+or run one off computations by simply providing them `csc 10 + 1.14 * ln(50)`
+
 ## Meta
 
 M. Zahash – zahash.z@gmail.com