initial convert to TS. No major logic changes, just type safety.

.eslintrc.js

@@ -0,0 +1,29 @@
+module.exports = {
+  root: true,
+  env: {
+    node: true
+  },
+  extends: [
+    'airbnb-base',
+    'plugin:@typescript-eslint/recommended',
+    'prettier/@typescript-eslint',
+    'plugin:prettier/recommended',
+  ],
+  parser: '@typescript-eslint/parser',
+  parserOptions: {
+    project: './tsconfig.json',
+    sourceType: 'module'
+  },
+  plugins: ['@typescript-eslint'],
+  settings: {
+    'import/extensions': ['.js', '.ts',],
+    'import/parsers': {
+      '@typescript-eslint/parser': ['.ts']
+    },
+    'import/resolver': {
+      node: {
+        extensions: ['.js', '.ts',]
+      }
+    }
+  }
+}