feat: add platform__list_resources into the system prompt

crates/goose/src/prompts/system.md

@@ -10,10 +10,12 @@ to interactions with sytems that are not currently active. The currently
 active systems are below. Each of these systems provides tools that are
 in your tool specification.
 
-The format of a tool is "{system_name}__{tool_name}", i.e. the system 
+The format of a tool is "{system_name}__{tool_name}", i.e. the system
 name followed by the tool name with '__' as the separator.
 
-By default, we add a tool called "platform__read_resource", which can 
+By default, we add two tools, one called "platform__list_resources"
+which can be used to list resources with URIs from all or from a specific
+system by name and one called "platform__read_resource", which can
 be used to read a resource URI from a system.
 
 # Systems: