Seg Reader

Added the ability to read Seg lumps from the WAD file.

src/types/seg.rs

@@ -0,0 +1,9 @@
+#[derive(Clone, Debug, PartialEq)]
+pub struct Seg {
+    pub start_vertex: i16,
+    pub end_vertex: i16,
+    pub angle: i16,
+    pub linedef: i16,
+    pub direction: i16,
+    pub offset: i16,
+}