Upgrade to GitHub-native Dependabot (#577)

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

.github/dependabot.yml

@@ -0,0 +1,31 @@
+version: 2
+updates:
+- package-ecosystem: pip
+  directory: "/"
+  schedule:
+    interval: daily
+  open-pull-requests-limit: 10
+  ignore:
+  - dependency-name: docutils
+    versions:
+    - "0.17"
+  - dependency-name: sphinx
+    versions:
+    - 3.4.3
+    - 3.5.0
+    - 3.5.1
+    - 3.5.2
+    - 3.5.3
+  - dependency-name: flake8
+    versions:
+    - 3.9.0
+  - dependency-name: pygments
+    versions:
+    - 2.7.4
+    - 2.8.0
+  - dependency-name: tox
+    versions:
+    - 3.21.2
+    - 3.21.3
+    - 3.21.4
+    - 3.22.0