Fixed-case for multi-sentence titles

In paper titles with multiple sentences, the first word of non-initial sentences should probably be ``d.

This happens e.g. here:
[How Good is Your Tokenizer? On the Monolingual Performance of Multilingual Language Models](https://aclanthology.org/2021.acl-long.243)

Using our official Anthology BibTeX with the ARR templates, "on" will appear in the bibliography as all-lowercase.

Reproduce the reported title-casing issue using the linked paper title, the official Anthology BibTeX, and the ARR templates. Trace the BibTeX title-generation entry point to determine where the first word of each non-initial sentence is handled; done means the bibliography renders “On” with fixed case rather than lowercase.

由索引模型根据 Issue 内容生成。