add multiline comment support

src/scanner.zig

@@ -153,7 +153,7 @@ pub const Scanner = struct {
     }
 
     fn peekNext(self: *Scanner) u8 {
-        if (self.current + 1 >= self.source.len) return 0;
+        if (self.current > self.source.len) return 0;
         return self.source[self.current];
     }
 
@@ -246,14 +246,27 @@ pub const Scanner = struct {
             '>' => self.makeMatchToken('=', .GreaterEqual, .Greater),
 
             '/' => blk: {
-                if (self.peekNext() == '/') {
+                var next = self.peekNext();
+                switch (next) {
+                    '/' => blk2: {
                         while (self.peek() != '\n' and !self.isAtEnd()) {
                             _ = self.advance();
                         }
 
-                    break :blk null;
+                        return null;
-                } else {
+                    },
-                    break :blk self.makeToken(.Slash);
+
+                    '*' => blk2: {
+                        while (self.peek() != '*' or self.peekNext() != '/') {
+                            _ = self.advance();
+                        }
+
+                        // consume the ending slash
+                        _ = self.advance();
+                        return null;
+                    },
+
+                    else => break :blk self.makeToken(.Slash),
                 }
             },