add(docs): Note default path to config in docs

[arya2]

Motivation

This PR makes it easier to find docs about the default config paths for macOS and Windows.

Closes #7964.

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Solution

Adds a note to the README, zebrad docs, ZebradConfig docs, and generate command output with a link to default path to preferences directory for macOS/Windows.

Review

Anyone can review.

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[teor2345]

Just some things I noticed in a quick skim.

[teor2345]

Thanks!

[teor2345]

Thanks!