add RedPenNet results (#637)

Co-authored-by: Sebastian Ruder <ruder.sebastian@gmail.com>

english/grammatical_error_correction.md

@@ -138,6 +138,7 @@ Since current state-of-the-art systems rely on as much annotated learner data as
 | GRECO (Qorib and Ng, EMNLP 2023) | 80.84 | [System Combination via Quality Estimation for Grammatical Error Correction](https://aclanthology.org/2023.emnlp-main.785) | [official](https://github.com/nusnlp/greco) |
 | ESC (Qorib et al., NAACL 2022) | 79.90| [Frustratingly Easy System Combination for Grammatical Error Correction](https://aclanthology.org/2022.naacl-main.143/) | [official](https://github.com/nusnlp/esc) |
 | TMTC (Lai et al., ACL Findings 2022) | 77.93 | [Type-Driven Multi-Turn Corrections for Grammatical Error Correction](https://aclanthology.org/2022.findings-acl.254) | [official](https://github.com/DeepLearnXMU/TMTC) |
+| RedPenNet (Didenko & Sameliuk, UNLP 2023) | 77.60 | [RedPenNet for Grammatical Error Correction: Outputs to Tokens, Attentions to Spans](https://aclanthology.org/2023.unlp-1.15/) | [official](https://github.com/WebSpellChecker/unlp-2023-shared-task) |
 | RoBERTa(L) + EditScorer (Sorokin, EMNLP 2022) | 77.1 | [Improved grammatical error correction by ranking elementary edits](https://aclanthology.org/2022.emnlp-main.785) | [official](https://github.com/AlexeySorokin/EditScorer) |
 | Sequence tagging + token-level transformations + two-stage fine-tuning, DeBERTa + ELECTRA + RoBERTa ensemble (Mesham et al., EACL 2023) | 76.17 | [An Extended Sequence Tagging Vocabulary for Grammatical Error Correction](https://aclanthology.org/2023.findings-eacl.119.pdf) | [Official](https://github.com/StuartMesham/gector_experiment_public) |
 | DeBERTa(L) + RoBERTa(L) + XLNet (Tarnavskyi et al., ACL 2022) | 76.05 | [Ensembling and Knowledge Distilling of Large Sequence Taggers for Grammatical Error Correction](https://aclanthology.org/2022.acl-long.266) | [Official](https://github.com/MaksTarnavskyi/gector-large) |