chore: Add myself to assignees for Dependabot PRs (#5972)

So I get notified about deps updates.

https://docs.github.com/en/code-security/tutorials/secure-your-dependencies/customizing-dependabot-prs#automatically-adding-assignees

.github/dependabot.yml

@@ -4,11 +4,17 @@ updates:
     directory: "/docker"
     schedule:
       interval: "weekly"
+    assignees:
+      - "Fijxu"
   - package-ecosystem: github-actions
     directory: /
     schedule:
       interval: "weekly"
+    assignees:
+      - "Fijxu"
   - package-ecosystem: "nix"
     directory: /nix
     schedule:
       interval: "weekly"
+    assignees:
+      - "Fijxu"