Validate range expressions

[nathcouret]

Add checks in range expression that the left operand is "less" than the right operand.

• specify an error message for range bounds validation
• (Optional) Add recovery behaviour

Sample code

const invalidResult = cronix("0 20-4 * * *");
// should be null
console.log(invalidResult.ast.value());
// Should have 1 error at semantic step with invalid range bounds
console.log(invalidResult.errors[1]);

Recovery behaviour

In the above snippet, we assume the user actually meant 4-20 instead of 20-4. Therefore the parser should be able to identify such mistake and accordingly fix it if the user desires it. That behaviour can be enabled via a flag in the parser's options.