Compiling typescript into a browser-friendly format results in `Uncaught TypeError: (void 0) is not a function`

I'm running into the below error (in browser):

index.ts:1 Uncaught TypeError: (void 0) is not a function
    at eval (index.ts:1)
    at Object../src/index.ts (main.js:96)
    at __webpack_require__ (main.js:20)
    at main.js:84
    at main.js:87

I'm having difficulty knowing how to investigate this error. It seems to be the same issue here: Getting error "Void 0 is not function" on browser when using webpack to bundle typescript file

What is this eval("(void 0)(... in the compiled output?

I'm trying to compile a 'simple' typescript script into a form that can be run by the browser.

The entire MCVE is at this repo: https://github.com/chrissound/newCha

I have the following webpack and typescript config:

webpack.config.js

const path = require('path');

module.exports = {
  mode: 'development',
  entry: './src/index.ts',
  module: {
    rules: [
      {
        test: /\.tsx?$/,
        use: 'ts-loader',
        exclude: /node_modules/
      }
    ]
  },
  resolve: {
    extensions: [ '.tsx', '.ts', '.js' ]
  },
  output: {
    filename: 'main.js',
    path: path.resolve(__dirname, 'dist')
  }
};

tsconfig.json

{
    "compilerOptions": {
        "sourceMap": true,
        "target": "es5",
        "outFile": "compiled.js",
        "declaration": true,
        "removeComments": true,
        "module": "system"
    },
    "include": [
        "src/*"
    ],

    "exclude": [
        "node_modules",
        "**/*.spec.ts"
    ]
}