feat(character): init Character struct

- u8 life, damage, and mana
- rodata string name

src/character.rs

@@ -0,0 +1,6 @@
+struct Character {
+    life: u8,
+    damage: u8,
+    mana: u8,
+    name: &'static str,
+}

src/main.rs

@@ -1,3 +1 @@
-fn main() {
+fn main() {}
-    println!("Hello, world!");
-}