Initial renovate config. (#356)

diff --git a/renovate.json b/renovate.json
new file mode 100644
index 0000000..4fa9493
--- /dev/null
+++ b/renovate.json
@@ -0,0 +1,5 @@
+{
+  "extends": [
+    "config:base",  ":preserveSemverRanges"
+  ]
+}