Add yamllint configuration

.yamllint

@@ -0,0 +1,17 @@
+# vi: ft=yaml
+extends: default
+
+rules:
+    indentation:
+        level: warning
+        indent-sequences: consistent
+    line-length:
+        # there are some bash -c "", so this is OK
+        max: 300
+        level: warning
+    comments:
+        min-spaces-from-content: 1
+    document-start:
+        present: false
+    truthy:
+        check-keys: false