[docs] SWPrecachePlugin info in docs/deployment.md

Created by: wodin

Is this a bug report?

Yes, it's a documentation bug. Would submit a pull request, but I'm not sure of the correct fix.

docusaurus/docs/deployment.md contains the following line with two problems:

options of the `SWPreachePlugin` [configuration](../config/webpack.config.prod.js).

1. I believe SWPreachePlugin should be SWPrecachePlugin (missing a c).
2. ../config/webpack.config.prod.js does not exist and I don't know where it can be found.