feat: implement ability to boot straigt to cartridge

src/cartridge.rs

@@ -0,0 +1,26 @@
+use std::fs::File;
+use std::io::{self, Read};
+use std::path::Path;
+
+#[derive(Debug, Clone)]
+pub struct Cartridge {
+    memory: Vec<u8>,
+}
+
+impl Cartridge {
+    pub fn new<P: AsRef<Path> + ?Sized>(path: &P) -> io::Result<Self> {
+        let mut memory = vec![];
+        let mut rom = File::open(path)?;
+        rom.read_to_end(&mut memory)?;
+
+        Ok(Self { memory })
+    }
+
+    pub fn read_byte(&self, addr: u16) -> u8 {
+        self.memory[addr as usize]
+    }
+
+    pub fn read_word(&self, addr: u16) -> u16 {
+        (self.memory[(addr + 1) as usize] as u16) << 8 | self.memory[addr as usize] as u16
+    }
+}