Fix clippy warning in lib

    warning: field assignment outside of initializer for an instance created with Default::default()
      --> src/lib.rs:81:9
       |
    81 |         ret.parse_cli = true;
       |         ^^^^^^^^^^^^^^^^^^^^^
       |
       = note: `#[warn(clippy::field_reassign_with_default)]` on by default
    note: consider initializing the variable with `Aoc { parse_cli: true, ..Default::default() }` and removing relevant reassignments
      --> src/lib.rs:80:9
       |
    80 |         let mut ret = Self::default();
       |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#field_reassign_with_default

src/lib.rs

@@ -77,9 +77,7 @@ pub struct Aoc {
 
 impl Aoc {
     pub fn new() -> Self {
-        let mut ret = Self::default();
-        ret.parse_cli = true;
-        ret
+        Aoc { parse_cli: true, ..Default::default() }
     }
 
     /// Set the year