chore: add deprecation notice

Fixes #284.

README.md

@@ -1,13 +1,22 @@
 # karma-firefox-launcher
 
 [![js-standard-style](https://img.shields.io/badge/code%20style-standard-brightgreen.svg?style=flat-square)](https://github.com/karma-runner/karma-firefox-launcher)
- [![npm version](https://img.shields.io/npm/v/karma-firefox-launcher.svg?style=flat-square)](https://www.npmjs.com/package/karma-firefox-launcher) [![npm downloads](https://img.shields.io/npm/dm/karma-firefox-launcher.svg?style=flat-square)](https://www.npmjs.com/package/karma-firefox-launcher)
- [![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release)
+[![npm version](https://img.shields.io/npm/v/karma-firefox-launcher.svg?style=flat-square)](https://www.npmjs.com/package/karma-firefox-launcher) [![npm downloads](https://img.shields.io/npm/dm/karma-firefox-launcher.svg?style=flat-square)](https://www.npmjs.com/package/karma-firefox-launcher)
+[![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release)
 
 [![Build Status](https://img.shields.io/travis/karma-runner/karma-firefox-launcher/master.svg?style=flat-square)](https://travis-ci.org/karma-runner/karma-firefox-launcher) [![Dependency Status](https://img.shields.io/david/karma-runner/karma-firefox-launcher.svg?style=flat-square)](https://david-dm.org/karma-runner/karma-firefox-launcher) [![devDependency Status](https://img.shields.io/david/dev/karma-runner/karma-firefox-launcher.svg?style=flat-square)](https://david-dm.org/karma-runner/karma-firefox-launcher#info=devDependencies)
 
 > Launcher for Mozilla Firefox.
 
+## `karma-firefox-launcher` is deprecated and is not accepting new features or general bug fixes.
+
+See [deprecation notice for `karma`](https://github.com/karma-runner/karma#karma-is-deprecated-and-is-not-accepting-new-features-or-general-bug-fixes).
+
+[Web Test Runner](https://modern-web.dev/docs/test-runner/overview/),
+[`jasmine-browser-runner`](https://github.com/jasmine/jasmine-browser-runner),
+and [`playwright-test`](https://github.com/hugomrdias/playwright-test) provide
+browser-based unit testing solutions which can be used as a direct alternative.
+
 ## Installation
 
 The easiest way is to keep `karma-firefox-launcher` as a devDependency in your `package.json`.
@@ -19,19 +28,24 @@ npm install karma-firefox-launcher --save-dev
 ```
 
 ## Configuration
+
 ```js
 // karma.conf.js
-module.exports = function(config) {
+module.exports = function (config) {
   config.set({
-    plugins: [
-      require('karma-firefox-launcher')
+    plugins: [require("karma-firefox-launcher")],
+    browsers: [
+      "Firefox",
+      "FirefoxDeveloper",
+      "FirefoxAurora",
+      "FirefoxNightly",
     ],
-    browsers: ['Firefox', 'FirefoxDeveloper', 'FirefoxAurora', 'FirefoxNightly'],
-  })
-}
+  });
+};
 ```
 
 You can pass list of browsers as a CLI argument too:
+
 ```bash
 karma start --browsers Firefox,Chrome
 ```
@@ -43,11 +57,11 @@ To run Firefox in headless mode, append `Headless` to the version name, e.g. `Fi
 You can specify the location of the Firefox executable using the following
 environment variables:
 
-* `FIREFOX_BIN` (for browser `Firefox` or `FirefoxHeadless`)
-* `FIREFOX_DEVELOPER_BIN` (for browser `FirefoxDeveloper` or
+- `FIREFOX_BIN` (for browser `Firefox` or `FirefoxHeadless`)
+- `FIREFOX_DEVELOPER_BIN` (for browser `FirefoxDeveloper` or
   `FirefoxDeveloperHeadless`)
-* `FIREFOX_AURORA_BIN` (for browser `FirefoxAurora` or `FirefoxAuroraHeadless`)
-* `FIREFOX_NIGHTLY_BIN` (for browser `FirefoxNightly` or
+- `FIREFOX_AURORA_BIN` (for browser `FirefoxAurora` or `FirefoxAuroraHeadless`)
+- `FIREFOX_NIGHTLY_BIN` (for browser `FirefoxNightly` or
   `FirefoxNightlyHeadless`)
 
 ### Custom Firefox location
@@ -72,6 +86,7 @@ customLaunchers: {
 ```
 
 ### Custom Preferences
+
 To configure preferences for the Firefox instance that is loaded, you can specify a custom launcher in your Karma
 config with the preferences under the `prefs` key:
 
@@ -89,6 +104,7 @@ customLaunchers: {
 ```
 
 ### Loading Firefox Extensions
+
 If you have extensions that you want loaded into the browser on startup, you can specify the full path to each
 extension in the `extensions` key:
 
@@ -127,9 +143,8 @@ for the `em:id` tag under the `Description` tag. If your extension manifest look
 
 Then you should name your extension `[email protected]`.
 
-----
+---
 
 For more information on Karma see the [homepage].
 
-
 [homepage]: https://karma-runner.github.io