docs(plugins) IgnorePlugin new syntax and options (#2721)

Author: EugeneHlushko

src/content/plugins/ignore-plugin.md

@@ -7,19 +7,38 @@ contributors:
   - EugeneHlushko
 ---
 
-Prevent generation of modules for `import` or `require` calls matching the following regular expressions:
+IgnorePlugin prevents generation of modules for `import` or `require` calls matching the regular expressions or filter functions:
 
-- `requestRegExp` A RegExp to test the request against.
-- `contextRegExp` (optional) A RegExp to test the context (directory) against.
+## Using regular expressions
 
-``` js
+- `requestRegExp`: A RegExp to test the request against.
+- `contextRegExp`: (optional) A RegExp to test the context (directory) against.
+
+```javascript
+new webpack.IgnorePlugin({requestRegExp, contextRegExp});
+// old way, deprecated in webpack v5
 new webpack.IgnorePlugin(requestRegExp, [contextRegExp]);
 ```
 
-The following examples demonstrate a few ways this plugin can be used.
+## Using filter functions
+
+- `checkContext(context)` A Filter function that receives context as the argument, must return boolean.
+- `checkResource(resource)` A Filter function that receives resource as the argument, must return boolean.
 
+```javascript
+new webpack.IgnorePlugin({
+  checkContext (context) {
+    // do something with context
+    return true|false;
+  },
+  checkResource (resource) {
+    // do something with resource
+    return true|false;
+  }
+});
+```
 
-## Ignore Moment Locales
+## Example of ignoring Moment Locales
 
 As of [moment](https://momentjs.com/) 2.18, all locales are bundled together with the core library (see [this GitHub issue](https://github.com/moment/moment/issues/2373)). 
 
@@ -37,8 +56,11 @@ require('./locale/' + name);
 
 ...your first regexp must match that `'./locale/'` string. The second `contextRegExp` parameter is then used to select specific directories from where the import took place. The following will cause those locale files to be ignored:
 
-```js
-new webpack.IgnorePlugin(/^\.\/locale$/, /moment$/);
+```javascript
+new webpack.IgnorePlugin({
+  requestRegExp: /^\.\/locale$/,
+  contextRegExp: /moment$/
+});
 ```
 
 ...which means "any require statement matching `'./locale'` from any directories ending with `'moment'` will be ignored.