prepare modules for the next days

src/cli/commands/day021.rs

@@ -0,0 +1,8 @@
+use crate::cli::PathBuf;
+use crate::util::read_lines;
+
+pub fn subcmd_day021(file: &Option<PathBuf>, alt: &bool) {
+    if let Ok(lines) = read_lines(file.as_ref().unwrap().as_path()) {
+
+    }
+}