ci: add workflow dispatch trigger

.github/workflows/cachix.yaml

@@ -1,5 +1,6 @@
 name: "Build packages and push to cache"
 on:
+  workflow_dispatch:
   push:
     paths: 
       - outputs/pkgs/**

.github/workflows/check.yaml

@@ -1,5 +1,6 @@
 name: "Nix Flake Check"
 on:
+  workflow_dispatch:
   push:
     branches:
       - main
@@ -16,6 +17,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
+      - name: Configure git
+        uses: git config --global url."https://github.com/".insteadOf "git@github.com:"
       - name: Setup Nix
         uses: DeterminateSystems/nix-installer-action@main
       - name: Magic Nix Cache