Adding new example counting formulas and errors (#6)

base/src/lib.rs

@@ -18,6 +18,12 @@
 //! ```rust
 #![doc = include_str!("../examples/hello_world.rs")]
 //! ```
+//!
+//! In this example, we demonstrate our ability to handle formulas and errors:
+//!
+//! ```rust
+#![doc = include_str!("../examples/formulas_and_errors.rs")]
+//! ```
 
 pub mod calc_result;
 pub mod cell;