Allow forwarding benchmark's stdout to hyperfine

This change makes it possible to forward the stdout of the command the
user tries to benchmark to hyperfine's stdout using the `--print-stdout`
flag.

This should be irrelevant for most use-cases, however it makes it
possible to get some crude benchmarks of terminal emulators similar to
what's currently often done with `time cat file`.

src/hyperfine/types.rs

@@ -89,6 +89,9 @@ pub struct HyperfineOptions {
 
     /// What color mode to use for output
     pub output_style: OutputStyleOption,
+
+    /// Forward benchmark's stdout to hyperfine's stdout
+    pub print_stdout: bool,
 }
 
 impl Default for HyperfineOptions {
@@ -100,6 +103,7 @@ impl Default for HyperfineOptions {
             failure_action: CmdFailureAction::RaiseError,
             preparation_command: None,
             output_style: OutputStyleOption::Full,
+            print_stdout: false,
         }
     }
 }