Migrate Renovate config (#90)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/renovate.json

@@ -3,10 +3,11 @@
   "extends": [
     "config:recommended"
   ],
-  "regexManagers": [
+  "customManagers": [
     {
-      "fileMatch": [
-        "(^|/)(.*\\.)?Dockerfile$"
+      "customType": "regex",
+      "managerFilePatterns": [
+        "/(^|/)(.*\\.)?Dockerfile$/"
       ],
       "matchStrings": [
         "#\\s*renovate:\\s*datasource=(?<datasource>.*?) depName=(?<depName>.*?)( versioning=(?<versioning>.*?))?\\sENV .*?_VERSION=\"?(?<currentValue>.*?)\"?\\s"