Update the configuration samples to match the current backend

[kosmosac]

Summary

• use the current singular names for all built-in plugins
• include the economy and task plugins
• use and document the current delivery rule action names
• add the missing manage_announcements permission
• use the supported {content} variable for announcement forwarding
• include the optional Discord role IDs in the JSON sample

The changes keep config_sample.json and docs/config.jsonc aligned with the current backend without changing runtime behavior.

Closes #9