Paper missing from SIGMORPHON 2021 proceedings

## Option 2: Revision or erratum

[LiWilson_sigmorphon2021.pdf](https://github.com/acl-org/acl-anthology/files/9004991/LiWilson_sigmorphon2021.pdf)

- [x] I have attached the revised PDF or erratum to this issue
- [x] I have written a brief description of the changes below

It seems the attached paper (Li and Wilson, 2021) appears in the SIGMORPHON proceedings on github: https://sigmorphon.github.io/workshops/2021/2021_SIGMORPHON_Proceedings.pdf
It, however, does not appear in the acl anthology: https://aclanthology.org/volumes/2021.sigmorphon-1/

To avoid confusion, the same authors submitted two papers to the workshop: a Li & Wilson (system JHU-SFU), and a Wilson & Li (system JHU) paper.
The Wilson & Li appears in the anthology already, but the Li and Wilson (which is attached) does not.

Is there a way to fix this and add the attached paper to the anthology?