Speed up drone check (#1324)

reduce clone depth to minimum

migrate to drone 1.x syntax

Co-authored-by: max.mehl <max.mehl@fsfe.org>

.drone.yml

@@ -1,6 +1,13 @@
-pipeline:
-  syntaxcheck:
+kind: pipeline
+type: docker
+name: default
+
+clone:
+  depth: 1
+
+steps:
+  - name: syntaxcheck
     image: vsasyan/xmllint
     commands:
-        - find . -type f \( -iname "*.xhtml" -o -iname "*.xml" -o -iname "*.xsl" \) -exec xmllint --noout {} +
-        - bash tools/check-non-en-frontpage.sh news
+    - find . -type f \( -iname "*.xhtml" -o -iname "*.xml" -o -iname "*.xsl" \) -exec xmllint --noout {} +
+    - bash tools/check-non-en-frontpage.sh news