[5.1] Add link to JED - schema plugins category in schema plugin form

[jgerman-bot]

New language relevant PR in upstream repo: joomla/joomla-cms#42747 Here are the upstream changes:

Click to expand the diff!

diff --git a/administrator/language/en-GB/plg_system_schemaorg.ini b/administrator/language/en-GB/plg_system_schemaorg.ini
index 1a09bab4e6adf..189a8c2a5f227 100755
--- a/administrator/language/en-GB/plg_system_schemaorg.ini
+++ b/administrator/language/en-GB/plg_system_schemaorg.ini
@@ -11,6 +11,7 @@ PLG_SYSTEM_SCHEMAORG_BASETYPE_OPTION_PERSON="Person"
 PLG_SYSTEM_SCHEMAORG_FIELD_SCHEMA_DESCRIPTION="Structured data is a standardised format for organising and representing information on the web. It provides a way to describe the content and meaning of data in a structured manner, making it easier for search engines and other applications to understand and process the information. <a href=\"https://schema.org\" target=\"_blank\" rel=\"noopener noreferrer\">More information on schema.org</a>."
 PLG_SYSTEM_SCHEMAORG_FIELD_SCHEMA_DESCRIPTION_NOT_CONFIGURATED="To use the schema.org functionality, you have to configure the plugin first. Please contact an administrator of the page to get it configured."
 PLG_SYSTEM_SCHEMAORG_FIELD_SCHEMA_DESCRIPTION_NOT_CONFIGURATED_ADMIN="To use the schema.org functionality, you have to configure the plugin first. Please select <a href=\"index.php?option=com_plugins&amp;task=plugin.edit&amp;extension_id=%s\" target=\"_blank\">this link to open the plugin</a>, configure and save."
+PLG_SYSTEM_SCHEMAORG_FIELD_SCHEMA_EXTEND_JED_DESC="<strong>Need more Schema types?</strong> Extend with <a href=\"https://extensions.joomla.org/category/core-enhancements/schema-plugins\" target=\"_blank\" rel=\"noopener noreferrer\">Schema Plugins from Joomla! Extension Directory</a>."
 PLG_SYSTEM_SCHEMAORG_FIELD_SCHEMA_LABEL="Schema"
 PLG_SYSTEM_SCHEMAORG_FIELD_SCHEMA_TYPE_LABEL="Schema Type"
 PLG_SYSTEM_SCHEMAORG_IMAGE_LABEL="Image"
diff --git a/plugins/system/schemaorg/forms/schemaorg.xml b/plugins/system/schemaorg/forms/schemaorg.xml
index e012a47479f39..332f2970a1547 100755
--- a/plugins/system/schemaorg/forms/schemaorg.xml
+++ b/plugins/system/schemaorg/forms/schemaorg.xml
@@ -21,6 +21,14 @@
 				<option value="None">JNONE</option>
 			</field>
 
+			<field
+				name="extendJed"
+				type="note"
+				class="alert alert-info d-block w-100"
+				parentclass="order-last"
+				description="PLG_SYSTEM_SCHEMAORG_FIELD_SCHEMA_EXTEND_JED_DESC"
+			/>
+
 		</fieldset>
 	</fields>
 </form>
diff --git a/plugins/system/schemaorg/src/Extension/Schemaorg.php b/plugins/system/schemaorg/src/Extension/Schemaorg.php
index c0d46f05e8664..c76b395afab8b 100644
--- a/plugins/system/schemaorg/src/Extension/Schemaorg.php
+++ b/plugins/system/schemaorg/src/Extension/Schemaorg.php
@@ -164,6 +164,9 @@ public function onContentPrepareForm(Model\PrepareFormEvent $event)
 
             $form->setFieldAttribute('schemainfo', 'description', $infoText, 'schema');
 
+            $form->setFieldAttribute('extendJed', 'type', 'hidden', 'schema');
+            $form->setFieldAttribute('extendJed', 'class', 'hidden', 'schema');
+
             return;
         }