Update README

README.txt → README.md

@@ -12,15 +12,17 @@ consumed by frontend builds.
 REQUIREMENTS
 ------------
 
- * This module is an extension to the core JSON:API module and requires Drupal
- 8.7 or greater.
+ * PHP 7.4 (note: this requirement is not enforced by `composer.json` due to
+   Drupal core's support of PHP 7.3. Requiring PHP 7.4 breaks testing against
+   due to core's [`composer.json`](https://git.drupalcode.org/project/drupal/-/blob/9.3.x/composer.json#L51).)
+ * Drupal 9+
 
 
 INSTALLATION
 ------------
 
  * Install as any contributed Drupal module. For further information, visit
-   https://www.drupal.org/docs/8/extending-drupal-8/installing-drupal-8-modules
+   [Installing modules](https://www.drupal.org/docs/extending-drupal/installing-modules).
 
 
 CONFIGURATION
@@ -39,10 +41,10 @@ MAINTAINERS
 -----------
 
 Current maintainers:
- * Timo Kirkkala (kirkkala) - https://www.drupal.org/u/kirkkala
+ * Christopher C. Wells (wells) - https://www.drupal.org/u/wells
+ * Andrii Podanenko (podarok) - https://www.drupal.org/u/podarok
 
 This project has been sponsored by:
- * Wunder.io
-   Wunder is Europe's largest digital agency specialising in Drupal projects,
-   web service design and business consulting. We work with private and public
-   sectors.
+ * Cascade Public Media - https://www.drupal.org/cascade-public-media
+ * ITCare - https://www.drupal.org/itcare
+ * Wunder.io - https://www.drupal.org/wunder