feat: add auto highlighter plugin and follow some advice from the rust-analyzer

[shulaoda]

This plugin is very simple, just to solve this issue web-infra-dev/rspress#1043. I think putting it in plugin_toc may avoid an unnecessary loop operation, but in the end, I decided to add a plugin for future maintenance.
In addition, I also removed some unnecessary code based on the prompts from the rust-analyzer.

[SoonIter]

LGTM, I think there is also a TODO point that we need to handle the default alias to get better DX

```md
```

```markdown
```

Maybe it is more appropriate to do this work on the js side.
https://github.com/web-infra-dev/rspress/blob/10799e72a7b592898eab5ef0a1cd08adaaf4cf4c/packages/shared/src/runtime-utils/index.ts#L11

[shulaoda]

Maybe it is more appropriate to do this work on the js side. https://github.com/web-infra-dev/rspress/blob/10799e72a7b592898eab5ef0a1cd08adaaf4cf4c/packages/shared/src/runtime-utils/index.ts#L11

Yes, I have completed the relevant operations and will submit them later in rspress.