Merge pull request #1297 from emberjs/update-TS-support

Author: rwjblue

.github/workflows/ci-build.yml

@@ -72,6 +72,8 @@ jobs:
       matrix:
         ts-version:
           - 4.7
+          - 4.8
+          - 4.9
           - next
 
     steps:

README.md

@@ -9,7 +9,7 @@ Compatibility
 - Ember.js v4 or above
 - Ember CLI v4 or above
 - Node.js v14 or above
-- TypeScript 4.7
+- TypeScript 4.7, 4.8, and 4.9
   - SemVer policy: [simple majors](https://www.semver-ts.org/#simple-majors)
   - the public API is defined by [API.md](./API.md).
 
@@ -21,7 +21,7 @@ Installation
 #### yarn
 ```bash
 yarn add --dev @ember/test-helpers
-````
+```
 
 #### npm
 ```bash