Servo was never meant to be a full engine replacement for mainline Firefox; whatever Rust code could be implemented/useful for Firefox was ported already.

However, regarding Servo specifically, there are contributions on their GitHub[1] and the stewardship of the project is now under the Linux Foundation[2].

[1] https://github.com/servo/servo/commits/master [2] https://blog.servo.org/2020/11/17/servo-home/