Handlebars.js: 打字稿类型：`knownHelpers` 不允许自定义助手

在提交问题之前，请先检查以下几点：

• [x] 请不要为安全问题打开问题。 相反，请在https://www.npmjs.com/advisories/report?package=handlebars提交报告
• [x] 看看https://github.com/wycats/handlebars.js/blob/master/CONTRIBUTING.md
• [x] 在https://github.com/wycats/handlebars.js/blob/master/FAQ.md阅读常见问题解答
• [x] 使用https://jsfiddle.net/9D88g/47/上的 jsfiddle-template 来重现问题或错误

这可能会帮助您更快地获得解决方案。
对于错误，拥有一个测试用例失败的 PR 会很棒。

目前Handlebar 的打字稿定义不允许在knownHelper选项上指定自定义帮助程序。

因此，要将knownHelpersOnly选项与自定义助手一起使用，您必须强制转换knownHelpers以绕过打字稿检查；

function given(...args: any[]): string {
  const options = args.pop();

  if (options.fn) {
    let complete = true;
    const proxy = new Proxy(this, {
      get(context, prop: string): object {
        if (!(prop in context)) {
          complete = false;
        }

        return context[prop];
      },
    });

    const text = options.fn(proxy);

    return complete ? text : '';
  }

  return args.some((a: string): boolean => !a) ? '' : args.join(' ');
}

const templateOptions = {
  helpers: {
    first,
  },
};
const compilerOptions = {
  knownHelpers: { first: true } as unknown, // Without this `unknown` compilation fails
  knownHelpersOnly: true,
};

Hanblebars.compile('My nice template {{first "text"}}', compilerOptions)({}, templateOptions);

产生的错误（不使用unknown强制转换）如下：

TypeScript diagnostics (customize using `[jest-config].globals.ts-jest.diagnostics` option):
    src/index.test.ts:93:41 - error TS2345: Argument of type '{ knownHelpers: { first: boolean; }; knownHelpersOnly: boolean; }' is not assignable to parameter of type 'CompileOptions'.
      Types of property 'knownHelpers' are incompatible.
        Type '{ first: boolean; }' has no properties in common with type '{ helperMissing?: boolean; blockHelperMissing?: boolean; each?: boolean; if?: boolean; unless?: boolean; with?: boolean; log?: boolean; lookup?: boolean; }'.

CompilerOptions不应该有以下定义吗？：

interface CompileOptions {
  data?: boolean;
  compat?: boolean;
  knownHelpers?: { [name: string]: boolean };
  knownHelpersOnly?: boolean;
  noEscape?: boolean;
  strict?: boolean;
  assumeObjects?: boolean;
  preventIndent?: boolean;
  ignoreStandalone?: boolean;
  explicitPartialContext?: boolean;
}

（我没有得到什么吗？如果这是正确的解决方案，我愿意发送 PR）