Magento2 : Create Category attribute

/** @var EavSetup $eavSetup */
$eavSetup = $this->eavSetupFactory->create(['setup' => $setup]);


/**
* Add attributes to the eav/attribute
*/
$eavSetup->addAttribute(
\Magento\Catalog\Model\Category::ENTITY,
'external_link',
[
'group' => 'General',
'type' => 'varchar',
'label' => 'External Link',
'input' => 'text',
'global' => \Magento\Catalog\Model\Resource\Eav\Attribute::SCOPE_GLOBAL,
'visible' => true,
'required' => false,
'user_defined' => true,
'default' => '',
]
);