DrupalOrg plugin warnings when viewing Compose tips page

Problem/Motivation

When viewing the Compose tips page, the settings may not be available when the DrupalOrg plugin is enabled.

This does not occur for the External links plugin, which the Drupalorg plugin class extends.

Warning: Undefined array key "settings" in Drupal\freelinking\Plugin\freelinking\DrupalOrg->getIndicator() (line 32 of modules/contrib/freelinking/src/Plugin/freelinking/DrupalOrg.php).

Drupal\freelinking\Plugin\freelinking\DrupalOrg->getIndicator() (Line: 181)
Drupal\freelinking\Plugin\Filter\Freelinking->tips() (Line: 274)

Steps to reproduce

1. Install freelinking
2. Create a text format with Freelinking DrupalOrg plugin configured
3. Create a node type with a formatted text field configured to use the text format
4. Visit /filter/tips

Proposed resolution

Fix the issue and write a functional test to assert tips output.

The tips page does not instantiate the plugin with configuration array, but with settings. Apparently the only thing that used its settings was DrupalOrg plugin.

Remaining tasks

- None