Add funtion getchildren

[karan96108]

Add child node traversal methods to Element class

Problem

Currently users need to switch between requests-html and lxml.etree to work with child nodes,
creating unnecessary complexity.

Implementation

Added two methods to Element class:

• children property - Returns list of direct child elements
• getchildren() method - Provides lxml.etree compatibility

Breaking Changes

None. Adds new functionality while maintaining backwards compatibility.

Usage

# Using property
for child in element.children:
    print(child.tag)

# Using lxml-compatible method 
for child in element.getchildren():
    print(child.tag)