Docs: Icon search in dark theme

### Current behaviour
While searching in the docs for an Icon using dark theme the text input displays whiteish text on white background (css overwrites dark theme).

### Expected behaviour
While searching in the docs for an Icon using dark theme the text input should display whiteish text on a dark background.

### How to reproduce?
Turn on dark mode, go to https://callstack.github.io/react-native-paper/docs/guides/icons/#1-an-icon-name.
At the end of the paragraph open the collapsible list ("See the list of supported icons") and type (i.e. "bug") in the provided text input - the written text is invisible.

### Preview
Currently live in the docs.

### What have you tried so far?
Manually switching off in inspect mode property `background-color: #f0f0f0;` in `.icons-list-searchbar` seems to work properly.

### Your Environment

| software | version
| --------------------- | -------
| firefox | 144.0 (64-bit)
| chromium | 141.0.7390.54 (Official Build)

在文档源代码中搜索选择器 `.icons-list-searchbar` 以及 issue 中引用的图标指南。在深色模式下重现该搜索，然后检查该选择器的主题样式，并验证在可折叠的图标列表中，输入的文本在深色背景上仍然清晰可读。

由索引模型根据 Issue 内容生成。