chore(deps): update eslint and related tooling

Upgrade ESLint and related dependencies to latest major versions, including
@typescript-eslint, prettier, and esbuild. Replace legacy .eslintrc.js config
with new flat config (eslint.config.mjs). Update Node.js engine to 18+ and
add .node-version file. Adjust esbuild config to use Node 18 and output path
from package.json. Remove obsolete files and update package-lock.json to
reflect new dependency tree.

Author: dansomething

.eslintignore

@@ -0,0 +1 @@
+18

.eslintrc.js

@@ -1,5 +1,9 @@
+import fs from 'fs';
 import * as esbuild from 'esbuild';
 
+const loadJSON = (path) => JSON.parse(fs.readFileSync(new URL(path, import.meta.url)));
+const data = loadJSON('package.json');
+
 const options = {
   entryPoints: ['src/index.ts'],
   bundle: true,
@@ -8,8 +12,8 @@ const options = {
   mainFields: ['module', 'main'],
   external: ['coc.nvim'],
   platform: 'node',
-  target: 'node16',
-  outfile: 'lib/index.js',
+  target: 'node18',
+  outfile: data.main,
   // https://esbuild.github.io/api/#log-level
   logLevel: process.env.NODE_ENV === 'development' ? 'info' : 'error',
 };

.node-version

@@ -0,0 +1,29 @@
+import tseslint from '@typescript-eslint/eslint-plugin';
+import tsparser from '@typescript-eslint/parser';
+import prettierPlugin from 'eslint-plugin-prettier';
+import prettierConfig from 'eslint-config-prettier';
+
+export default [
+  {
+    files: ['src/**/*.ts'],
+
+    languageOptions: {
+      parser: tsparser,
+      sourceType: 'module',
+    },
+
+    plugins: {
+      '@typescript-eslint': tseslint,
+      prettier: prettierPlugin,
+    },
+
+    rules: {
+      ...tseslint.configs.recommended.rules,
+      ...prettierConfig.rules,
+      '@typescript-eslint/no-unused-vars': 'warn',
+      'no-console': 'warn',
+      semi: ['error', 'always'],
+      'prettier/prettier': 'error',
+    },
+  },
+];