Add search terms to many commands (#5096)

crates/nu-command/src/strings/char_.rs

@@ -171,6 +171,10 @@ impl Command for Char {
         "Output special characters (e.g., 'newline')."
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["line break", "newline", "Unicode"]
+    }
+
     fn examples(&self) -> Vec<Example> {
         vec![
             Example {

crates/nu-command/src/strings/str_/downcase.rs

@@ -27,6 +27,10 @@ impl Command for SubCommand {
         "downcases text"
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["lower case", "lowercase"]
+    }
+
     fn run(
         &self,
         engine_state: &EngineState,

crates/nu-command/src/strings/str_/upcase.rs

@@ -24,6 +24,10 @@ impl Command for SubCommand {
         "upcases text"
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["uppercase", "upper case"]
+    }
+
     fn run(
         &self,
         engine_state: &EngineState,