refactor docker deployment

Reviewed-on: http://git.simonis.lol/projects/file-explorer/pulls/17

.gitea/workflows/build.yaml

@@ -9,15 +9,12 @@ jobs:
   build:
     runs-on: remote
     steps:
-      - uses: https://git.simonis.lol/actions/checkout@v4
-      - uses: https://git.simonis.lol/actions/login@v1
-        with:
-          registry: git.simonis.lol
-          username: ${{ vars.DOCKER_USER }}
-          password: ${{ vars.DOCKER_PW }}
 
-      - name: build
+      - name: Checkout
-        run: docker build -t git.simonis.lol/projects/file-explorer:latest .
+        uses: https://git.simonis.lol/actions/checkout@v2
 
-      - name: push
+      - name: Build
-        run: docker push git.simonis.lol/projects/file-explorer:latest
+        run: docker buildx build -t git.simonis.lol/projects/file-explorer:latest .
+
+      - name: Push
+        run: docker push git.simonis.lol/projects/file-explorer:latest