Search terms for compact command (#12864)

# Description

There was a question in Discord today about how to remove empty rows
from a table. The user found the `compact` command on their own, but I
realized that there were no search terms on the command. I've added
'empty' and 'remove', although I subsequently figured out that 'empty'
is found in the "usage" anyway. That said, I don't think it hurts to
have good search terms behind it regardless.

# User-Facing Changes

Just the help

# Tests + Formatting

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

# After Submitting

crates/nu-command/src/filters/compact.rs

@@ -31,6 +31,10 @@ impl Command for Compact {
         "Creates a table with non-empty rows."
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["empty", "remove"]
+    }
+
     fn run(
         &self,
         engine_state: &EngineState,