SIMID-308: Add spec guidance for cryptographically secure session ids.

[nchavez324]

This is the spec fix for #308.

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💥 Error: 400 Bad Request 💥

PR Preview failed to build. (Last tried on Feb 25, 2022, 6:15 PM UTC).

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🚨 CSS Spec Preprocessor - CSS Spec Preprocessor is the web service used to build Bikeshed specs.

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Error running preprocessor, returned code: 2.
FATAL ERROR: Line 513 isn't indented enough (needs 1 indent) to be valid Markdown:
"  * New messages [[#simid-creative-expandNonlinear]], [[#simid-creative-collapseNonlinear]], and [[#simid-player-collapseNonlinear]] and related data."
 ✘  Did not generate, due to fatal errors

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