Create Dependabot config file

dependabot-preview[bot] · jrolfs · commit e6c619a43774 · 2020-07-18T00:55:59.000-07:00
diff --git a/.github/dependabot.yml b/.github/dependabot.yml
@@ -0,0 +1,8 @@
+version: 2
+updates:
+- package-ecosystem: npm
+  directory: "/"
+  schedule:
+    interval: daily
+  pull-request-branch-name:
+    separator: "-"
