chore: add cert-manager renovate group

.github/renovate.json5

@@ -61,6 +61,14 @@
       "commitMessageExtra": "to {{#if isSingleVersion}}v{{{newVersion}}}{{else}}{{{newValue}}}{{/if}}",
       "matchUpdateTypes": ["major", "minor", "patch"]
     },
+    {
+      "description": "Group Cert-Manager image (for CRDs) and chart",
+      "groupName": "Cert-Manager",
+      "matchPackagePatterns": ["cert-manager"],
+      "matchDatasources": ["docker", "helm"],
+      "group": { "commitMessageTopic": "{{{groupName}}} group" },
+      "separateMinorPatch": true
+    },
     // add labels according to package and update types
     {
       "matchDatasources": ["docker"],