Add explanation of fixable in --statistics command (#13774)

Co-authored-by: Micha Reiser <[email protected]>

Author: sbrugman

crates/ruff/src/printer.rs

@@ -417,6 +417,10 @@ impl Printer {
                         statistic.name,
                     )?;
                 }
+
+                if any_fixable {
+                    writeln!(writer, "[*] fixable with `ruff check --fix`",)?;
+                }
                 return Ok(());
             }
             OutputFormat::Json => {

crates/ruff/tests/integration_test.rs

@@ -979,6 +979,7 @@ fn show_statistics() {
     exit_code: 1
     ----- stdout -----
     1	F401	[*] unused-import
+    [*] fixable with `ruff check --fix`
 
     ----- stderr -----
     "###);