Add testing for ember-source 5.8 and 5.12

Author: NullVoxPopuli

.github/workflows/ci.yml

@@ -152,6 +152,8 @@ jobs:
           - ember-4.8
           - ember-4.12
           - ember-5.4
+          - ember-5.8
+          - ember-5.12
           - ember-release
           - ember-beta
           - ember-canary

test-app/config/ember-try.js

@@ -57,6 +57,22 @@ module.exports = async function () {
           },
         },
       },
+      {
+        name: 'ember-5.8',
+        npm: {
+          devDependencies: {
+            'ember-source': '~5.8.0',
+          },
+        },
+      },
+      {
+        name: 'ember-5.12',
+        npm: {
+          devDependencies: {
+            'ember-source': '~5.12.0',
+          },
+        },
+      },
       {
         name: 'ember-release',
         npm: {