Add docker deps to Renovate

.github/renovate.json5

@@ -17,6 +17,11 @@
       "commitMessageTopic": "Helm chart {{depName}}",
       "separateMinorPatch": true
     },
+    {
+      "datasources": ["docker"],
+      "commitMessageTopic": "Docker image {{depName}}",
+      "separateMinorPatch": true
+    },
     {
       "commitMessagePrefix": "[{{{parentDir}}}]",
       "branchTopic": "{{{parentDir}}}-{{{depNameSanitized}}}-{{{newMajor}}}{{#if isPatch}}.{{{newMinor}}}{{/if}}.x{{#if isLockfileUpdate}}-lockfile{{/if}}",