Add docker action cache and platforms input

Signed-off-by: trivernis <trivernis@protonmail.com>

.github/workflows/docker.yml

@@ -2,6 +2,11 @@ name: Docker
 
 on:
   workflow_dispatch:
+    inputs:
+      platforms:
+        description: 'Platforms to build the container for'
+        required: true
+        default: 'linux/amd64,linux/arm/v7,linux/arm64'
 
 jobs:
   multi:
@@ -35,7 +40,7 @@ jobs:
         with:
           context: .
           file: ./Dockerfile
-          platforms: linux/amd64,linux/arm/v7,linux/arm64
+          platforms: ${{github.events.inputs.platforms}}
           push: true
           tags: |
             trivernis/snekcloud-server:alpine