fix: add support for custom selectors like data-theme

[GavinXue]

When update to version 0.9.1, the feature of controlling themes by using data-theme is no longer supported. You can refer to this repository demonstration for a better understanding: repository demo.

This PR introduces support for the following scenario.

selectors: {
  light: '[data-theme="light"]',
  dark: '[data-theme="dark"]',
},

[Dunqing]

Thanks!