add dependabot yaml

.github/dependabot.yaml

@@ -0,0 +1,24 @@
+# https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+# mostly from https://github.com/microsoft/torchgeo/blob/main/.github/dependabot.yml
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    groups:
+      # torchvision pins torch, must update in unison
+      torch:
+        patterns:
+          - "torch"
+          - "torchvision"
+    ignore:
+      # setuptools releases new versions almost daily
+      - dependency-name: "setuptools"
+        update-types: ["version-update:semver-patch"]
+      # segmentation-models-pytorch pins timm, must update in unison
+      - dependency-name: "timm"