不索引指定后缀的文件和指定名字的文件

### Please make sure of the following things

- [x] I have read the [documentation](https://alist.nn.ci).
- [x] I'm sure there are no duplicate issues or discussions.
- [x] I'm sure this feature is not implemented.
- [x] I'm sure it's a reasonable and popular requirement.

### Description of the feature / 需求描述

比如jpg，png等图片后缀不进行索引。
以及"预览图"这种文件夹不进行索引。

如果用来存图片的话会导致数据库暴增索引缓慢

### Suggested solution / 实现思路

可以在自动更新索引中加一个正则匹配？

### Additional context / 附件

_No response_