Merge pull request MyIntervals#228 from oliverklee/task/php-8

Add linting with PHP 8 to the CI builds

Author: sabberworm

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        php-version: [ '5.6', '7.0', '7.1', '7.2', '7.3', '7.4' ]
+        php-version: [ '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0' ]
 
     steps:
       - name: Checkout