Declare custom modules & themes compatible with Drupal 9

web/modules/custom/geo_citation/geo_citation.info.yml

@@ -1,7 +1,7 @@
 name: "GEO Citations"
 description: "Formatted credit line for Grassroots Economic Organizing collective's original articles."
 type: module
-core: 8.x
+core_version_requirement: ^8 || ^9
 dependencies:
   - drutopia_article
 package: Custom

web/modules/custom/geo_upgrade/geo_upgrade.info.yml

@@ -1,7 +1,7 @@
 name: Geo Upgrade
 type: module
 description: Customization of Drupal 7 to Drupal 8 upgrade migration.
-core: 8.x
+core_version_requirement: ^8 || ^9
 package: Migration
 dependencies:
   - migrate_drupal

web/themes/custom/geofresco/geofresco.info.yml

@@ -3,7 +3,7 @@ description: Customization of Drutopia's Bulma-based Octavia theme for Grassroot
 type: theme
 base theme: octavia
 package: Custom
-core: 8.x
+core_version_requirement: ^8 || ^9
 
 logo: images/geo-logo-sun-road.png