feat: publish container image (#82)

Use `goreleaser` and `ko` to automatically build and publish container
images in the release workflow. The images are published to
`ghcr.io/apricote/hcloud-upload-image`.

Co-authored-by: Ilja Malachowski <malahovskiy.in@gmail.com>

.goreleaser.yaml

@@ -7,7 +7,8 @@ before:
     - ./scripts/completions.sh
 
 builds:
-  - env:
+  - id: default
+    env:
       - CGO_ENABLED=0
     goos:
       - linux
@@ -21,7 +22,7 @@ builds:
       - -X {{ .ModulePath }}/internal/version.versionPrerelease=
 
 archives:
-  - format: tar.gz
+  - formats: [ "tar.gz" ]
     # this name template makes the OS and Arch compatible with the results of `uname`.
     name_template: >-
       {{ .ProjectName }}_
@@ -33,7 +34,7 @@ archives:
     # use zip for windows archives
     format_overrides:
       - goos: windows
-        format: zip
+        formats: [ "zip" ]
 
     files:
       - README.md
@@ -104,9 +105,23 @@ aurs:
       install -Dm644 "./completions/hcloud-upload-image.zsh" "${pkgdir}/usr/share/zsh/site-functions/_hcloud-upload-image"
       install -Dm644 "./completions/hcloud-upload-image.fish" "${pkgdir}/usr/share/fish/vendor_completions.d/hcloud-upload-image.fish"
 
+kos:
+  - id: container-images
+    build: default
+    repositories:
+      - ghcr.io/apricote
+    platforms:
+      - linux/amd64
+      - linux/arm64
+    base_import_paths: true
+    labels:
+      org.opencontainers.image.source: https://github.com/apricote/hcloud-upload-image
+    tags:
+      - latest
+      - "{{.Tag}}"
 
 snapshot:
-  name_template: "{{ .Version }}-dev+{{ .ShortCommit }}"
+  version_template: "{{ .Version }}-dev+{{ .ShortCommit }}"
 
 changelog:
   # Generated by release-please