Merge pull request #90 from voxpupuli/add-el-9

add RedHat/Rocky/AlmaLinux/CentOS 9 support

Author: bastelfreak

metadata.json

@@ -37,19 +37,28 @@
     {
       "operatingsystem": "RedHat",
       "operatingsystemrelease": [
-        "8"
+        "8",
+        "9"
       ]
     },
     {
       "operatingsystem": "Rocky",
       "operatingsystemrelease": [
-        "8"
+        "8",
+        "9"
       ]
     },
     {
       "operatingsystem": "AlmaLinux",
       "operatingsystemrelease": [
-        "8"
+        "8",
+        "9"
+      ]
+    },
+    {
+      "operatingsystem": "CentOS",
+      "operatingsystemrelease": [
+        "9"
       ]
     },
     {