Improve search generation script

[hasezoey]

Summary

This PR aims to improve the search generation script, by doing:

• move the script from /docs to /scripts (because it is not a browser script)
• disconnect on error (had it hanging for me)
• add useful error when no config is found
• change to use /docs/api/file.html over /docs/api.html (re docs(api.pug): change to redirect to mongoose API page #12223 (comment) & Make sure search generation works with 7.0 #13033)
• use Object.entries over creating a one-time use array
• disable strictQuery warning

[vkarpov15]

Thanks 👍