Add ESLint and lint a bunch

eslint.config.mjs

@@ -0,0 +1,40 @@
+import eslint from '@eslint/js';
+import tseslint from 'typescript-eslint';
+import stylistic from '@stylistic/eslint-plugin';
+
+export default tseslint.config(
+	eslint.configs.recommended,
+	tseslint.configs.recommendedTypeChecked,
+	{
+		languageOptions: {
+			parserOptions: {
+				projectService: true,
+				tsconfigRootDir: import.meta.dirname,
+			},
+		},
+	},
+	stylistic.configs.customize({
+		indent: 'tab',
+		quotes: 'single',
+		semi: true,
+		braceStyle: '1tbs',
+	}),
+	{
+		rules: {
+			'@stylistic/max-len': ['error', {
+				code: 120,
+			}],
+			'@typescript-eslint/no-empty-object-type': 'off',
+		},
+	},
+	{
+		ignores: [
+			'dist',
+			'build',
+			'api-sketch.ts',
+			'build.mjs',
+			'append-namespace.mjs',
+			'eslint.config.mjs',
+		]
+	}
+);