update formatting examples for comma change

[Jamiras]

Numeric formatters were updated in rcheevos 12.0 to output commas. This updates the documentation to reflect that change and adds a note on how to provide unformatted numbers in a backwards compatible way.

[greptile-apps]

Greptile Summary

Updates Rich Presence formatting examples for comma-separated numbers and documents unformatted-number compatibility and null-terminated character strings.

Confidence Score: 5/5

The documentation changes appear safe to merge.

No concrete, changed-code-triggered failures were established.

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