ci: create image for x64 architecture

Author: lschloetterer

.github/workflows/build-image.yml

@@ -14,7 +14,7 @@ permissions:
 
 env:
   IMAGE_NAME: ghcr.io/${{ github.repository }}
-  PLATFORMS: linux/arm/v7
+  PLATFORMS: linux/amd64,linux/arm/v7
 
 jobs:
   build-image:

README.md

@@ -5,7 +5,7 @@ Version numbers are copied from upstream.
 
 Image details:
 - Uses *alpine* image flavor
-- *ARMv7* architecture (e.g. Raspberry Pi)
+- *x64* and *ARMv7* architecture (e.g. Raspberry Pi)
 
 Pull with this image name: 
 ```