Implements feature request #4134 by adding the ability to specify custom URL parameters for LanguageTool requests.

Problem

Previously, users could only configure the LanguageTool server URL but had no way to pass additional parameters like level=picky for stricter grammar checking, motherTongue=es for better suggestions, or custom rule configurations. This limited the ability to take advantage of LanguageTool's advanced features.

Solution

This PR adds a new "URL Parameters" field in the LanguageTool configuration section that allows users to specify any additional parameters to be sent with grammar check requests.

Key Changes

• Configuration Structure: Added languageToolURLParams field to GrammarCheckerConfig struct
• User Interface: Added labeled input field with helpful tooltip showing parameter examples
• Network Layer: Modified POST request building to append custom parameters with smart formatting
• Integration: Properly registered configuration option with backward compatibility

Usage Examples

Users can now enter parameters like:

• level=picky - Enable stricter grammar checking
• motherTongue=es&level=picky - Combine multiple parameters
• disabledRules=WHITESPACE_RULE,COMMA_RULE - Disable specific rules
• enabledRules=CUSTOM_RULE - Enable specific custom rules

Technical Implementation

The implementation automatically handles parameter formatting:

Before (existing behavior):

POST: language=en&text=Hello%20world

After (with parameters):

POST: language=en&text=Hello%20world&level=picky&motherTongue=es

The feature includes smart parameter handling that automatically adds the "&" prefix if not present, ensuring proper URL parameter formatting regardless of how users enter the parameters.

Backward Compatibility

• Empty parameter field maintains existing behavior unchanged
• No impact on existing configurations
• Changes take effect immediately without requiring restart

This enhancement enables users to fully customize their LanguageTool experience while maintaining the simplicity of the existing configuration interface.

Fixes #4134

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