Enhancement appium image locating

[hassineabd]

Implements

• Added image locating strategy using base64 encoded images for Appium.
• Implemented _find_by_image function to support image-based element finding.
• Added _is_image_locator function to determine if a locator is an image.

Changes

• Modified the find method to call _is_image_locator and determine the strategy based on whether the locator is an image.