properly handle escaped newlines in quoted strings

src/utils/strings.rs

@@ -302,7 +302,8 @@ pub(crate) fn parse_quoted_string<I: Iterator<Item = Token>>(
                 };
 
                 if first.kind == '\n' {
-                    return Err(("Expected escape sequence.", first.pos()).into());
+                    toks.next();
+                    continue;
                 }
 
                 if first.kind.is_ascii_hexdigit() {

tests/str-escape.rs

@@ -172,3 +172,8 @@ error!(
     escape_sequence_does_not_fit_inside_char,
     "a {\n  color: \\110000;\n}\n", "Error: Invalid escape sequence."
 );
+test!(
+    escaped_newline_in_quoted_string,
+    "a {\n  color: \"foo\\\nbar\";\n}\n",
+    "a {\n  color: \"foobar\";\n}\n"
+);