Add Cirrus CI (#1025)

Add Cirrus CI to speed up validation of Play Store and F-Droid descriptions

Signed-off-by: mueller-ma <mueller-ma@users.noreply.github.com>

.cirrus.yml

+container:
+    image: python
+    cpu: 1
+    memory: 100M
+
+task:
+    name: Validate Play Store and F-Droid descriptions
+    play-stable-script: python3 assets/store_descriptions/generate_and_validate.py play
+    play-beta-script: python3 assets/store_descriptions/generate_and_validate.py playBeta
+    fdroid-stable-script: python3 assets/store_descriptions/generate_and_validate.py fdroid
+    fdroid-beta-script: python3 assets/store_descriptions/generate_and_validate.py fdroidBeta

.travis.yml

@@ -51,11 +51,6 @@ jobs:
       env:
         - desc="Uploads to GitHub"
       if: branch != l10n-crowdin AND tag != "-fdroid$" AND tag IS present
-    - stage: test
-      script: python3 assets/store_descriptions/generate_and_validate.py fdroidBeta
-      env:
-        - desc="Validate strings"
-      if: tag != "-fdroid$"
     - stage: deploy
       script: bash travis/prepare-deploy.sh
       if: tag IS present AND tag != "-fdroid$"