Add regexManagers to Renovate config

.editorconfig

@@ -13,8 +13,8 @@ charset = utf-8
 trim_trailing_whitespace = true
 insert_final_newline = true
 
-[composer.{json,lock}]
-indent_size = 4
+[renovate.json]
+indent_size = 2
 
 [{Makefile,**.mk}]
 # Use tabs for indentation (Makefiles require tabs)

.github/renovate.json

@@ -1,5 +1,14 @@
 {
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": [
     "config:base"
+  ],
+  "regexManagers": [
+    {
+      "fileMatch": ["(^|/|\\.)Dockerfile$"],
+      "matchStrings": ["ENV MAILPIT_VERSION=(?<currentValue>.*?)\n"],
+      "depNameTemplate": "axllent/mailpit",
+      "datasourceTemplate": "github-releases"
+    }
   ]
 }