dsh-tax-bonus: Year-End Bonus Income Tax Calculation Plugin

The `dsh-tax-bonus` plugin for DeepSeek Harness (DSH) is designed for financial calculations and provides local calculation of income tax on year-end bonuses. Maintained by uckkk, it is implemented in pure Node.js, has no network dependencies, and supports precise parameter-based calculations while returning detailed results. Users can install it via command and use the `tax_bonus` tool to perform calculations. Because it runs entirely locally, the plugin effectively avoids network latency and request failures, making it well suited for tax-related tasks.