Added ability to read WAD directory

src/wad/header.rs

@@ -0,0 +1,21 @@
+pub struct Header {
+    pub wad_id: String,
+    pub num_lumps: u32,
+    pub dir_offset: u32,
+}
+
+use crate::utils::{read_ascii, read_u32_le};
+
+impl Header {
+    pub fn read_data(data: &[u8]) -> Self {
+        let id = read_ascii(&data[..4]);
+        let lumps = read_u32_le(&data[4..8]);
+        let offset = read_u32_le(&data[8..12]);
+
+        Self {
+            wad_id: id,
+            num_lumps: lumps,
+            dir_offset: offset,
+        }
+    }
+}