DOC Document adding the help plugin to TinyMCEConfig (#840)

Author: GuySartorelli

en/08_Changelogs/6.2.0.md

@@ -91,6 +91,7 @@ If you have implemented a custom requirements backend, we recommend updating it
 
 ### Other new features and enhancements {#other-new}
 
+- The `help` plugin is now added by default to all [`TinyMCEConfig`](api:SilverStripe\TinyMCE\TinyMCEConfig) instances. If you were adding it manually, you can remove that custom code. If for some reason you don't want that plugin in one of your configs, you can use [`TinyMCEConfig::disablePlugins()`](api:SilverStripe\TinyMCE\TinyMCEConfig::disablePlugins()) to remove it - but be aware that it is extremely useful for screen reader users to keep this plugin installed.
 - [`HTML::createTag()`](api:SilverStripe\View\HTML::createTag()) now supports value-less boolean attributes. For example if you pass `HTML::create('input', ['readonly' => true])`, the result will be `<input readonly>`. Previously it would output as `<input readonly="1">`.
 - The built-in session handlers [`FileSessionHandler`](api:SilverStripe\Control\SessionHandler\FileSessionHandler), [`CacheSessionHandler`](api:SilverStripe\Control\SessionHandler\CacheSessionHandler), and [`DatabaseSessionHandler`](api:SilverStripe\Control\SessionHandler\DatabaseSessionHandler) all now validate the session ID `PHPSESSID` to ensure it matches a valid format, otherwise a `RuntimeException` will be thrown.
 - [`Hierarchy::duplicateWithChildren()`](api:SilverStripe\ORM\Hierarchy\Hierarchy::duplicateWithChildren()) used to set new sort values for duplicated children - it now uses the sort values from the original records.