feat: Add Dependabot for GHA and Renovate for pixi

Author: chrisburr

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

renovate.json

@@ -0,0 +1,14 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": [
+    "config:recommended",
+    ":dependencyDashboard",
+    "group:allNonMajor"
+  ],
+  "packageRules": [
+    {
+      "matchManagers": ["pixi"],
+      "groupName": "pixi dependencies"
+    }
+  ]
+}