fix: set explicit context for github actions docker builds

.github/workflows/stacks-blockchain-api.yml

@@ -496,6 +496,7 @@ jobs:
       - name: Build/Tag/Push Image
         uses: docker/build-push-action@v2
         with:
+          context: .
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           # Only push if (there's a new release on main branch, or if building a non-main branch) and (Only run on non-PR events or only PRs that aren't from forks)
@@ -504,6 +505,7 @@ jobs:
       - name: Build/Tag/Push Standalone Image
         uses: docker/build-push-action@v2
         with:
+          context: .
           file: docker/stx-rosetta.Dockerfile
           tags: ${{ steps.meta_standalone.outputs.tags }}
           labels: ${{ steps.meta_standalone.outputs.labels }}