fix: move GitHub Actions workflow directory (#2)

Moves the GitHub Actions workflow directory up a level to the appropriate location.

.github/workflows/devcontainer-build-and-push.yaml

@@ -0,0 +1,29 @@
+name: Dev Container Build and Push Image
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - "main"
+    tags:
+      - "v*.*.*"
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        id: checkout
+        uses: actions/checkout@v1
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v2
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Pre-build dev container image
+        uses: devcontainers/ci@v0.2
+        with:
+          subFolder: .github
+          imageName: ghcr.io/${{ github.repository }}
+          cacheFrom: ghcr.io/${{ github.repository }}
+          push: always