* feat: add browserless provider integration to native browser implementation
This PR adds support for the Browserless provider to the native browser implementation, expanding the available remote browser providers from 3 to 4.
## Changes Made
- **Added `connect_browserless()` function**: Implements session creation with Browserless API using environment variables for configuration
- **Updated provider routing**: Added "browserless" case to the main provider switch statement
- **Added session cleanup**: Implemented proper session termination using the stop URL returned by Browserless
- **Updated documentation**: Modified comments and error messages to include Browserless in the supported provider list
- **Environment variable support**: Added support for configurable Browserless settings including API key, URL, browser type, TTL, and stealth mode
## Implementation Details
- Uses standard Browserless session API with POST to create sessions and DELETE to terminate
- Supports both chromium and chrome browser types with validation
- Includes proper error handling for API failures and missing configuration
- Stores the stop URL as session_id for cleanup purposes
- Follows the existing provider pattern for consistency
Fixes#744
* fix: URL-encode API key in browserless session request
Use reqwest's .query() method instead of string-formatting the token
directly into the URL, matching the Node.js implementation's use of
encodeURIComponent. Prevents malformed URLs if the API key contains
special characters.
---------
Co-authored-by: ctate <366502+ctate@users.noreply.github.com>
