Add Support for Conditional Validation with `cond:field=value` Syntax

[abmercy035]

We need to implement conditional validation to allow rules to be applied only when certain conditions are met. This will enable more complex validation scenarios where some fields are only required or validated based on the values of other fields.

Problem to Solve:
Currently, all validation rules are applied unconditionally, which doesn't work for forms with conditional fields or business logic that depends on specific field values.

Acceptance Criteria:

• Implement cond:field=value syntax to conditionally apply rules
• Support for multiple conditions with AND/OR logic
• Support for comparison operators (=, !=, >, <, >=, <=)
• Support for nested field references in conditions
• Add comprehensive tests for conditional validation
• Update documentation with examples

Implementation Suggestions:

• Add a condition parser in the rule executor
• Implement a condition evaluator that checks if conditions are met before applying rules
• Support both simple equality and more complex comparisons

Example Usage:

const rules = [
  "shippingAddress-string-cond:needsShipping=true",
  "cardNumber-string-16-cond:paymentMethod=credit",
  "cvv-number-3-cond:paymentMethod=credit",
  "accountNumber-string-cond:paymentMethod=bank"
];

Labels: enhancement, conditional-validation, feature