Add JSHint

Add JSHint script:
https://github.com/jquery-boilerplate/jquery-boilerplate/blob/master/.jshintrc

The issue references a .jshintrc file from another project. First, check if the repository already has a .jshintrc or similar linting configuration. If not, copy the linked file and place it in the root directory. Then, add a script to package.json to run JSHint, likely targeting JavaScript files in the project. Verify by running the script to ensure it works without errors.

索引モデルが issue の本文から書いたものです。