docs: Fix a few typos

[timgates42]

There are small typos in:

• cli/parse-options.js
• cli/utils/create-auth-dbUrl.js
• docs/api/index.rst
• docs/developers/DOCS_STYLE.rst

Fixes:

• Should read persistence rather than persistance.
• Should read modifying rather than modifing.
• Should read individual rather than individial.
• Should read demonstrated rather than demostrated.

Semi-automated pull request generated by https://github.com/timgates42/meticulous/blob/master/docs/NOTE.md