Add cron to CI (#97)

diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index d79bc31..395251f 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -5,6 +5,8 @@
     branches: [ master ]
   pull_request:
     branches: [ master ]
+  schedule:
+    - cron: "0 0 * * 0"
 
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