Draft: Use latest markdownlint to enforce emphasis style

What does this MR do?

Enforce the standard for italics and bold in the docs:

• Italics use _ -> _italics_ -> italics
• Bold uses ** -> **bold** -> bold

This can now be checked with markdownlint, so this was an automated process by running the latest markdownlint with --fix:

• markdownlint --fix --config ../.markdownlint.yml '**/*.md'

Related issues

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