Basic usage

```rust use xyz_validator::{RqlValidator, ValidatorInterface};

fn main() { //Check if RQL statement is valid let rql_validator: Box = Box::new(RqlValidator::new());

let rql_statement = "or(and(eq(name,John),eq(surname,Smith)),eq(surname,Doe))".to_owned();
assert!(rql_validator.is_valid(rql_statement));

} ```