Add yamllint to pre-commit

Adding a hook to pre-commit to enforce a consistent style and remove the
hook check-yaml which only checks if a document is parsable and so
become redundant.

Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>

.yamllint.yaml

@@ -0,0 +1,8 @@
+---
+# https://yamllint.readthedocs.io/en/stable/index.html
+extends: default
+rules:
+  line-length:
+    max: 100
+  truthy:
+    check-keys: false