dx: consolidate dependabot PRs with catch-all groups (closes #57)

Add 'all-deps' catch-all group for npm packages not covered by the
existing angular/ngrx/nx/material groups, and a 'github-actions'
group so Actions updates batch into a single monthly PR.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: chrisjwalk-bot

.github/dependabot.yml

@@ -15,8 +15,13 @@ updates:
         patterns: ["@nx/*", "nx"]
       material:
         patterns: ["@angular/material", "@angular/cdk"]
+      all-deps:
+        patterns: ["*"]
 
   - package-ecosystem: github-actions
     directory: /
     schedule:
       interval: monthly
+    groups:
+      github-actions:
+        patterns: ["*"]