Add S3 storage configuration and client

.env.example

@@ -1,5 +1,9 @@
 # Copy this file to .env for local development. Use real, private values locally.
 NUXT_MONGODB_URI=mongodb://127.0.0.1:27017/music-v2
-NUXT_UPLOAD_DIR=./upload
 NUXT_PUBLIC_MEDIA_BASE_URL=https://s3-seaweedfs.lucasskt.dk/music
+NUXT_S3_ENDPOINT=https://s3-seaweedfs.lucasskt.dk
+NUXT_S3_BUCKET=music
+NUXT_S3_REGION=us-east-1
+NUXT_S3_ACCESS_KEY_ID=
+NUXT_S3_SECRET_ACCESS_KEY=
 NUXT_TOKEN_EXPIRE=1h