Update eslint from 8.57.1 to 10.0.3 with flat config migration

ESLint 10 drops the legacy eslintrc format, so migrate to flat config.
- Replace .eslintrc.json and .eslintignore with eslint.config.js
- Remove eslint-plugin-github (incompatible with eslint 10; its internal
  config only provided 3 DOM rules unused by this project)
- Update @typescript-eslint/* to 8.57.2 and eslint-plugin-jest to 29.x
- Add globals package for environment globals in flat config

eslint.config.js

@@ -0,0 +1,60 @@
+import tsParser from '@typescript-eslint/parser'
+import tsPlugin from '@typescript-eslint/eslint-plugin'
+import jestPlugin from 'eslint-plugin-jest'
+import globals from 'globals'
+
+export default [
+  {
+    ignores: ['dist/', 'lib/', 'node_modules/']
+  },
+  {
+    files: ['src/**/*.ts'],
+    languageOptions: {
+      parser: tsParser,
+      parserOptions: {
+        ecmaVersion: 9,
+        sourceType: 'module',
+        project: './tsconfig.json'
+      },
+      globals: {
+        ...globals.node,
+        ...globals.es2021
+      }
+    },
+    plugins: {
+      '@typescript-eslint': tsPlugin,
+      jest: jestPlugin
+    },
+    rules: {
+      'no-unused-vars': 'off',
+      '@typescript-eslint/no-unused-vars': 'error',
+      '@typescript-eslint/explicit-member-accessibility': ['error', {accessibility: 'no-public'}],
+      '@typescript-eslint/no-require-imports': 'error',
+      '@typescript-eslint/array-type': 'error',
+      '@typescript-eslint/await-thenable': 'error',
+      camelcase: 'off',
+      '@typescript-eslint/explicit-function-return-type': ['error', {allowExpressions: true}],
+      '@typescript-eslint/no-array-constructor': 'error',
+      '@typescript-eslint/no-empty-object-type': 'error',
+      '@typescript-eslint/no-explicit-any': 'off',
+      '@typescript-eslint/no-extraneous-class': 'error',
+      '@typescript-eslint/no-for-in-array': 'error',
+      '@typescript-eslint/no-inferrable-types': 'error',
+      '@typescript-eslint/no-misused-new': 'error',
+      '@typescript-eslint/no-namespace': 'error',
+      '@typescript-eslint/no-non-null-assertion': 'warn',
+      '@typescript-eslint/no-unnecessary-qualifier': 'error',
+      '@typescript-eslint/no-unnecessary-type-assertion': 'error',
+      '@typescript-eslint/no-useless-constructor': 'error',
+      '@typescript-eslint/prefer-for-of': 'warn',
+      '@typescript-eslint/prefer-function-type': 'warn',
+      '@typescript-eslint/prefer-includes': 'error',
+      '@typescript-eslint/prefer-string-starts-ends-with': 'error',
+      '@typescript-eslint/promise-function-async': ['error', {allowAny: true}],
+      '@typescript-eslint/require-array-sort-compare': 'error',
+      '@typescript-eslint/restrict-plus-operands': 'error',
+      semi: 'off',
+      '@typescript-eslint/unbound-method': 'error'
+    }
+  }
+]