Change eslint command in course website to match video

Currently, the course website text is using `npx eslint script.js` which doesn't match the file structure up to this point, or the video for this command. The file structure/video uses `npx eslint src/App.js`

[Line 33 in C-eslint.MD](https://github.com/btholt/complete-intro-to-react-v7/edit/main/lessons/03-js-tools/C-eslint.md#33)

Open lessons/03-js-tools/C-eslint.md at line 33 and compare the command with the file structure and corresponding video. Change the example to use src/App.js, then verify that the written command matches both the lesson context and video.

Written by the indexing model from the issue text.