update ci; add dependabot config

.github/dependabot.yaml

@@ -0,0 +1,12 @@
+# Dependabot configuration file.
+version: 2
+
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: monthly
+    groups:
+      github-actions:
+        patterns:
+          - "*"

.github/workflows/dart.yml

@@ -13,11 +13,11 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        sdk: [beta,stable]
+        sdk: [beta, stable]
 
     steps:
-      - uses: actions/checkout@v2
-      - uses: dart-lang/setup-dart@v1
+      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8
+      - uses: dart-lang/setup-dart@e51d8e571e22473a2ddebf0ef8a2123f0ab2c02c
         with:
           sdk: ${{ matrix.sdk }}
 

analysis_options.yaml

@@ -4,6 +4,8 @@ analyzer:
   exclude:
     - "doc/api/**"
     - "lib/mode/**"
+  errors:
+    deprecated_member_use: false
 
 linter:
   rules: