LibJS: Fix that a windows-style new line was not escaped properly

Author: https://github.com/davidot
Commit: 4cc95ae39d
Pull-request: https://github.com/SerenityOS/serenity/pull/9085
Reviewed-by: https://github.com/IdanHo
Reviewed-by: https://github.com/linusg ✅
Reviewed-by: https://github.com/trflynn89

Userland/Libraries/LibJS/Lexer.cpp

@@ -549,6 +549,9 @@ Token Lexer::next()
         while (m_current_char != stop_char && m_current_char != '\r' && m_current_char != '\n' && !is_eof()) {
             if (m_current_char == '\\') {
                 consume();
+                if (m_current_char == '\r' && m_position < m_source.length() && m_source[m_position] == '\n') {
+                    consume();
+                }
             }
             consume();
         }