scanner: add whitespace handling

src/new_scanner.zig

@@ -68,9 +68,30 @@ pub const Scanner = struct {
         }
     }
 
-    pub fn scanToken(self: *Scanner) !tokens.Token {
-        self.start = self.current;
+    fn peek(self: *Scanner) u8 {
+        if (self.isAtEnd()) return 0;
+        return self.source[self.current];
+    }
 
+    fn skipWhitespace(self: *Scanner) void {
+        while (true) {
+            var c = self.peek();
+            switch (c) {
+                ' ', '\r', '\t' => blk: {
+                    _ = self.advance();
+                },
+                '\n' => blk: {
+                    self.line += 1;
+                    _ = self.advance();
+                },
+                else => return,
+            }
+        }
+    }
+
+    pub fn scanToken(self: *Scanner) !tokens.Token {
+        self.skipWhitespace();
+        self.start = self.current;
         if (self.isAtEnd()) return self.makeToken(TokenType.EOF);
 
         var c = self.advance();