Add qwen model series to model list

Related to #7

This pull request introduces the qwen model series, including their pricing details, into the model list.

Adds a new file src/data/qwen.ts to define the qwen model series and their pricing, exporting a PlatformInterface object named price_qwen which includes model names, pricing for input and output tokens, and tags for each model.
Updates src/data/platform.ts to import the price_qwen object and add it to the platforms record, thereby integrating the qwen model series into the application. Additionally, a new tag 'qwen' is added to the ITag type to facilitate filtering and categorization.

For more details, open the Copilot Workspace session.

small-tou / llm-price