add beacon input to test script and mpc introduction

use only pointers out of circuit and handle errors properly

Export css and key files as prove input (#8)

* export and compute proof based on pk and vk files

* use css as an exported file as well

* refactor MPC command flags

* log file challenges when executing or verifying MPC

remove unused setup

Add export contract cmd (#3)

* add a command to export contract

* format code and cmd descriptions

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Co-authored-by: doubiliu <lmy0930@126.com>
Co-authored-by: txhsl <799498265@qq.com>

Add executable MPC command lines (#2)

* add mpc cmd template

* update cmd

* update cmd flags and descriptions

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Co-authored-by: doubiliu <lmy0930@126.com>