MAGETWO-90214 Configure TinyMCE editor (magento#1892)

Added new page, configure-tinymce-editor.md, and added in nav in WYSIWYG directory.

_data/toc/ui-components-guide.yml

@@ -163,18 +163,21 @@ pages:
         - label: WYSIWYG component
           versions: ["2.0","2.1","2.2"]
           url: ui_comp_guide/components/ui-wysiwyg.html
- 
+
         - label: WYSIWYG component
           versions: "2.3"
           url: ui_comp_guide/components/ui-wysiwyg.html
           children:
 
-            - label: Extension Points
-              url: ui_comp_guide/components/wysiwyg/extension-points/
-
             - label: Add Custom Editor
               url: ui_comp_guide/components/wysiwyg/add-custom-editor/
 
+            - label: Configure the TinyMCE editor
+              url: ui_comp_guide/components/wysiwyg/configure-tinymce-editor.html
+
+            - label: Extension Points
+              url: ui_comp_guide/components/wysiwyg/extension-points/
+
     - label: Concepts
       children:
 

guides/v2.3/ui_comp_guide/components/wysiwyg/configure-tinymce-editor.md

@@ -0,0 +1,35 @@
+---
+layout: default
+subgroup: howtos
+group: UI_Components_guide
+title: Configure the TinyMCE editor
+version: 2.3
+github_link: ui_comp_guide/howto/configure-tinymce-editor.md
+---
+You can extend and fully customize the TinyMCE editor to match the style and look-and-feel of your custom theme.
+This enables richer content editing capabilities and ensures that content created in the Page Builder <span term-uuid="98cf4fd5-59b6-4610-9c1f-b84c8c0abd97" class="glossary-term" data-toggle="popover">WYSIWYG</span> is seamlessly integrated and consistent with your other content.
+
+## Edit the module's `di.xml` file {#edit-di}
+
+Revise the `di.xml` file, adding the configuration settings as an argument to `Magento\PageBuilder\Model\Wysiwyg\DefaultConfigProvider`, to customize the TinyMCE editor present in Page Builder.
+
+The following code shows an example of configuration settings in the `di.xml` file that determine the font sizes available for selection and add a paragraph menu option associated with the `<p>` tag:
+
+```
+<type name="Magento\PageBuilder\Model\Wysiwyg\DefaultConfigProvider">
+    <arguments>
+        <argument name="additionalSettings" xsi:type="array">
+            <item name="fontsize_formats" xsi:type="string">10px 12px 14px 16px 18px 20px 24px 26px 28px 32px 34px 36px 38px 40px 42px 48px 52px 56px 64px 72px</item>
+            <item name="style_formats" xsi:type="array">
+                <item name="paragraph" xsi:type="array">
+                    <item name="title" xsi:type="string">Paragraph</item>
+                    <item name="block" xsi:type="string">p</item>
+                </item>
+            </item>
+      </argument>
+  </arguments>
+</type>
+```
+See a list of possibly TinyMCE settings on their [website](https://www.tinymce.com/docs/configure/).
+
+Once you have edited the `di.xml` file you can apply custom styling for the settings you implemented in the related CSS file.