CI: automatic builds (#1)

Adds CI pipelines to build and push the project to the Gitea Docker repository.

Co-authored-by: Julien Valverdé <julien.valverde@mailo.com>
Reviewed-on: https://git.jvalver.de/Thilawyn/protonmail-bridge-docker/pulls/1

.drone.yml

@@ -0,0 +1,51 @@
+kind: pipeline
+type: docker
+name: docker-build
+
+steps:
+- name: build
+  image: plugins/docker
+  settings:
+    registry: git.jvalver.de
+    username:
+      from_secret: username
+    password:
+      from_secret: password
+    repo: git.jvalver.de/thilawyn/protonmail-bridge-docker
+    dockerfile: build/Dockerfile
+    dry_run: true
+    context: build
+    autotag: true
+    compress: true
+    platform: linux/amd64
+
+trigger:
+  branch:
+    exclude:
+    - master
+
+
+---
+kind: pipeline
+type: docker
+name: docker-build-and-publish
+
+steps:
+- name: build-and-publish
+  image: plugins/docker
+  settings:
+    registry: git.jvalver.de
+    username:
+      from_secret: username
+    password:
+      from_secret: password
+    repo: git.jvalver.de/thilawyn/protonmail-bridge-docker
+    dockerfile: build/Dockerfile
+    context: build
+    autotag: true
+    compress: true
+    platform: linux/amd64
+
+trigger:
+  branch:
+  - master