Does docsearch's translates support string template placeholders?

## Describe the problem

Currently, the `translates` feature in DocSearch does not support string templates with placeholders. For example:
```json
{
"noResultText": "没有找到关于{{keyword}}的内容过"
}

The issue names DocSearch's translates feature but no file, test, or entry point. Start by locating that feature and its existing translation handling, then verify behavior for noResultText containing {{keyword}}. Done means string template placeholders are supported as shown.

Written by the indexing model from the issue text.