Replace entities package to fix TypeError with Hermes/Expo 54

[Copilot]

The entities package uses String.prototype.substr(), which was removed from modern JavaScript engines including Hermes (default in React Native/Expo 54). This causes TypeError: str.charAt is not a function when importing echarts v6.

Changes

• Removed entities dependency from package.json
• Implemented custom encodeXML function in src/svg/SVGCore.ts using substring() instead of deprecated substr()
• Maintains identical XML entity encoding behavior (special chars → named entities, non-ASCII → hex references)

Implementation

// Before: import { encodeXML } from 'entities';

// After: Custom implementation
function encodeXML(str: string): string {
  let ret = '';
  let lastIdx = 0;
  let match;
  while ((match = xmlReplacer.exec(str)) !== null) {
    // ... encoding logic
    ret += str.substring(lastIdx, i); // Uses substring() not substr()
  }
  return ret + str.substring(lastIdx); // Fixed: was str.substr(lastIdx)
}

This affects only SVG text node encoding for React Native SVG/Skia rendering.

Original prompt

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This section details on the original issue you should resolve

<issue_title>TypeError: str.charAt is not a function (it is undefined)</issue_title>
<issue_description>I am upgrading my project from expo 53 to expo 54,
in upgrade process, I am upgrading
@wuba/react-native-echarts from ^2.0.3 to latest
echarts from v5 to v6
and also skia

When build is successful and I try to run application, I get following error:

TypeError: str.charAt is not a function (it is undefined)

And it points to echarts import statement.

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes TypeError: str.charAt is not a function (it is undefined) #275

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