Update web/ samples to work with Flutter SDK (#134)

* add package:http dependency in dad_jokes

* add package:http dependency in filipino_cuisine

* don't build package:http demos until flutter/flutter#34858 is resolved

* update gallery

* update github_dataviz

* update particle_background

* don't build github_dataviz (uses package:http)

* update slide_puzzle

* update spinning_square

* update timeflow

* update vision_challenge

* update charts

* update dad_jokes

* update filipino cuisine

* ignore build output

* update timeflow and vision_challenge

* update slide_puzzle

* don't commit build/ directory

* move preview.png images to assets

* fix path url join

* update readme

* update web/readme.md

web/slide_puzzle/pubspec.yaml

@@ -1,31 +1,27 @@
 name: slide_puzzle
 
+version: 1.0.0
+
 environment:
-  sdk: ">=2.2.0 <3.0.0"
+  sdk: ">=2.0.0 <3.0.0"
 
 dependencies:
-  flutter_web: any
-  flutter_web_ui: any
-  provider: any
+  flutter:
+    sdk: flutter
 
 dev_dependencies:
+  flutter_test:
+    sdk: flutter
   pedantic: ^1.3.0
+  test: ^1.3.4
 
-  build_runner: any
-  build_web_compilers: any
+flutter:
+  uses-material-design: true
+  assets:
+    - asset/
+    - preview.png
 
-# flutter_web packages are not published to pub.dartlang.org
-# These overrides tell the package tools to get them from GitHub
-dependency_overrides:
-  flutter_web:
-    git:
-      url: https://github.com/flutter/flutter_web
-      path: packages/flutter_web
-  flutter_web_ui:
-    git:
-      url: https://github.com/flutter/flutter_web
-      path: packages/flutter_web_ui
-  provider:
-    git:
-      url: https://github.com/kevmoo/provider
-      ref: 5cf4521d4d6 # flutter_web, but v2
+  fonts:
+  - family: Plaster
+    fonts:
+    - asset: asset/fonts/plaster/Plaster-Regular.ttf