JSON String Support for Locators

[DavertMik]

This PR adds support for using JSON strings as locators in CodeceptJS. When a string starts with { and ends with }, it will be parsed as JSON and transformed into a locator object.

Changes Made

1. Enhanced Locator Class (lib/locator.js)

• Added parsedJsonAsString() method to handle JSON string parsing
• Supports simple key-value pairs as requested
• Falls back gracefully to normal string processing for invalid JSON
• Marks parsed locators as strict

2. Comprehensive Test Coverage (test/unit/locator_test.js)

• Added 12 test cases for JSON string parsing
• Tests cover various locator types: CSS, XPath, ID, custom locators
• Includes edge cases: whitespace, invalid JSON, aria-style locators
• Verifies equivalence between object and JSON string formats

Usage Examples

  // These are now equivalent:
  I.seeElement({ css: '#button' })
  I.seeElement('{"css": "#button"}')

  // Aria-style locators 
  I.seeElement('{"role": "button", "text": "Save"}')