Adopt WebDriverAbstract as a solution for active (JavaScript) websites (#3971)

* first working version

---------

Co-authored-by: Dag <me@dvikan.no>

docs/05_Bridge_API/04_WebDriverAbstract.md

@@ -0,0 +1,83 @@
+`WebDriverAbstract` extends [`BridgeAbstract`](./02_BridgeAbstract.md) and adds functionality for generating feeds
+from active websites that use XMLHttpRequest (XHR) to load content and / or JavaScript to
+modify content.
+It highly depends on the php-webdriver library which offers Selenium WebDriver bindings for PHP.
+
+- https://github.com/php-webdriver/php-webdriver (Project Repository)
+- https://php-webdriver.github.io/php-webdriver/latest/ (API)
+
+Please note that this class is intended as a solution for websites _that cannot be covered
+by the other classes_. The WebDriver starts a browser and is therefore very resource-intensive.
+
+# Configuration
+
+You need a running WebDriver to use bridges that depend on `WebDriverAbstract`.
+The easiest way is to start the Selenium server from the project of the same name:
+```
+docker run -d -p 4444:4444 --shm-size="2g" docker.io/selenium/standalone-chrome:latest
+```
+
+- https://github.com/SeleniumHQ/docker-selenium
+
+With these parameters only one browser window can be started at a time.
+On a multi-user site, Selenium Grid should be used
+and the number of sessions should be adjusted to the number of processor cores.
+
+Finally, the `config.ini.php` file must be adjusted so that the WebDriver
+can find the Selenium server:
+```
+[webdriver]
+
+selenium_server_url = "http://localhost:4444"
+```
+
+# Development
+
+While you are programming a new bridge, it is easier to start a local WebDriver because then you can see what is happening and where the errors are. I've also had good experience recording the process with a screen video to find any timing problems.
+
+```
+chromedriver --port=4444
+```
+
+- https://chromedriver.chromium.org/
+
+If you start rss-bridge from a container, then Chrome driver is only accessible
+if you call it with the `--allowed-ips` option so that it binds to all network interfaces.
+
+```
+chromedriver --port=4444 --allowed-ips=192.168.1.42
+```
+
+The **most important rule** is that after an event such as loading the web page
+or pressing a button, you often have to explicitly wait for the desired elements to appear.
+
+A simple example is the bridge `ScalableCapitalBlogBridge.php`.
+A more complex and relatively complete example is the bridge `GULPProjekteBridge.php`.
+
+# Template
+
+Use this template to create your own bridge.
+
+```PHP
+<?php
+
+class MyBridge extends WebDriverAbstract
+{
+    const NAME = 'My Bridge';
+    const URI = 'https://www.example.org';
+    const DESCRIPTION = 'Further description';
+    const MAINTAINER = 'your name';
+
+    public function collectData()
+    {
+        parent::collectData();
+
+        try {
+            // TODO
+        } finally {
+            $this->cleanUp();
+        }
+    }
+}
+
+```

docs/05_Bridge_API/index.md

@@ -8,6 +8,7 @@ Base class | Description
 -----------|------------
 [`BridgeAbstract`](./02_BridgeAbstract.md) | This class is intended for standard _Bridges_ that need to filter HTML pages for content.
 [`FeedExpander`](./03_FeedExpander.md) | Expand/modify existing feed urls
-[`XPathAbstract`](./04_XPathAbstract.md) | This class is meant as an alternative base class for bridge implementations. It offers preliminary functionality for generating feeds based on _XPath expressions_.
+[`WebDriverAbstract`](./04_WebDriverAbstract) |
+[`XPathAbstract`](./05_XPathAbstract) | This class is meant as an alternative base class for bridge implementations. It offers preliminary functionality for generating feeds based on _XPath expressions_.
 
 For more information about how to create a new _Bridge_, read [How to create a new Bridge?](./01_How_to_create_a_new_bridge.md)