Update and fix lints, bump min SDK to Dart 3.1 (#204)

.github/workflows/test-package.yml

diff --git a/.github/workflows/test-package.yml b/.github/workflows/test-package.yml
index 4823c1f..7655b33 100644
--- a/.github/workflows/test-package.yml
+++ b/.github/workflows/test-package.yml
@@ -47,7 +47,7 @@
       matrix:
         # Add macos-latest and/or windows-latest if relevant for this package.
         os: [ubuntu-latest, windows-latest]
-        sdk: [3.0, dev]
+        sdk: [3.1, dev]
     steps:
       - uses: actions/checkout@a5ac7e51b41094c92402da3b24376905380afc29
       - uses: dart-lang/setup-dart@f0ead981b4d9a35b37f30d36160575d60931ec30

CHANGELOG.md

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d1987e6..e1e361b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.0.2-wip
+
+- Require Dart 3.1
+
 ## 1.0.1
 
 - Update `ExpressionsProcessor.processFont` to handle null expressions.

pubspec.yaml

diff --git a/pubspec.yaml b/pubspec.yaml
index c54495d..290ad26 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: csslib
-version: 1.0.1
+version: 1.0.2-wip
 description: A library for parsing and analyzing CSS (Cascading Style Sheets).
 repository: https://github.com/dart-lang/csslib
 
@@ -7,13 +7,13 @@
   - css
 
 environment:
-  sdk: ^3.0.0
+  sdk: ^3.1.0
 
 dependencies:
   source_span: ^1.8.0
 
 dev_dependencies:
-  dart_flutter_team_lints: ^2.0.0
+  dart_flutter_team_lints: ^3.0.0
   path: ^1.8.0
   term_glyph: ^1.2.0
   test: ^1.16.0

test/testing.dart

diff --git a/test/testing.dart b/test/testing.dart
index 15421bf..2c76e58 100644
--- a/test/testing.dart
+++ b/test/testing.dart
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// Common definitions used for setting up the test environment.
-library testing;
+library;
 
 import 'package:csslib/parser.dart';
 import 'package:csslib/visitor.dart';

test/third_party_samples_test.dart

diff --git a/test/third_party_samples_test.dart b/test/third_party_samples_test.dart
index 9abb2bb..f4aee70 100644
--- a/test/third_party_samples_test.dart
+++ b/test/third_party_samples_test.dart
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 @TestOn('vm')
-library samples_test;
+library;
 
 import 'dart:io';