Updating tutorial samples to Dart v2

anagram/.gitignore

@@ -0,0 +1,9 @@
+# Files and directories created by pub
+.dart_tool/
+.packages
+
+# Conventional directory for build outputs
+build/
+
+# Directory created by dartdoc
+doc/api/

anagram/analysis_options.yaml

@@ -0,0 +1,8 @@
+# Defines a default set of lint rules enforced for
+# projects at Google. For details and rationale,
+# see https://github.com/dart-lang/pedantic#enabled-lints.
+include: package:pedantic/analysis_options.yaml
+
+linter:
+  rules:
+    - omit_local_variable_types