use caching for docker builds (#1340)

* try pulling for cached layers

* use cache-from and cache-to

* empty commit

* add readme

* use specific cache tags

* also cache from main

.github/workflows/ghcr.yml

@@ -30,7 +30,7 @@ jobs:
 
       - name: Log-in to ghcr.io
         run: echo "${{ secrets.GITHUB_TOKEN }}" | docker login ghcr.io -u ${{ github.actor }} --password-stdin
-        
+
       - name: Delete huge unnecessary tools folder
         run: rm -rf /opt/hostedtoolcache