Implemented invalid character checks

src/build/token/Tokenize.go

@@ -22,6 +22,8 @@ func Tokenize(buffer []byte) List {
 
 	for i < len(buffer) {
 		switch buffer[i] {
+		// Whitespace
+		case ' ', '\t':
 		// Texts
 		case '"':
 			start := i
@@ -118,6 +120,9 @@ func Tokenize(buffer []byte) List {
 				tokens = append(tokens, Token{Operator, position, buffer[position:i]})
 				continue
 			}
+
+			// Invalid characters
+			tokens = append(tokens, Token{Invalid, i, buffer[i : i+1]})
 		}
 
 		i++