Improve internal documentation of save command (#5704)

- Example for `--append` mode.
- Search terms for redirection

crates/nu-command/src/filesystem/save.rs

@@ -20,7 +20,16 @@ impl Command for Save {
     }
 
     fn search_terms(&self) -> Vec<&str> {
-        vec!["save", "write", "write_file"]
+        vec![
+            "write",
+            "write_file",
+            "append",
+            "redirection",
+            "file",
+            "io",
+            ">",
+            ">>",
+        ]
     }
 
     fn signature(&self) -> nu_protocol::Signature {
@@ -214,12 +223,17 @@ impl Command for Save {
     fn examples(&self) -> Vec<Example> {
         vec![
             Example {
-                description: "Save a string to foo.txt in current directory",
+                description: "Save a string to foo.txt in the current directory",
                 example: r#"echo 'save me' | save foo.txt"#,
                 result: None,
             },
             Example {
-                description: "Save a record to foo.json in current directory",
+                description: "Append a string to the end of foo.txt",
+                example: r#"echo 'append me' | save --append foo.txt"#,
+                result: None,
+            },
+            Example {
+                description: "Save a record to foo.json in the current directory",
                 example: r#"echo { a: 1, b: 2 } | save foo.json"#,
                 result: None,
             },