Add deps and config to update example with new build system

pkgs/markdown/build.yaml

diff --git a/pkgs/markdown/build.yaml b/pkgs/markdown/build.yaml
new file mode 100644
index 0000000..54b1fde
--- /dev/null
+++ b/pkgs/markdown/build.yaml
@@ -0,0 +1,22 @@
+# See https://github.com/dart-lang/build/tree/master/build_web_compilers#configuration
+targets:
+  $default:
+    builders:
+      build_web_compilers|dart2js_archive_extractor:
+        options:
+          # Ensures --dump-info .dart.js.info.json file is preserved.
+          # Useful to track compiled size change
+          filter_outputs: false
+      build_web_compilers|entrypoint:
+        # These are globs for the entrypoints you want to compile.
+        generate_for:
+        - example/**.dart
+        options:
+          dart2js_args:
+            - --dump-info
+            - --minify
+            - --no-frequency-based-minification
+            - --no-source-maps
+            - --show-package-warnings
+            - --trust-primitives
+            - --trust-type-annotations

pkgs/markdown/lib/src/version.dart

diff --git a/pkgs/markdown/lib/src/version.dart b/pkgs/markdown/lib/src/version.dart
index db17d9f..fd7256d 100644
--- a/pkgs/markdown/lib/src/version.dart
+++ b/pkgs/markdown/lib/src/version.dart
@@ -1,2 +1,2 @@
 /// The current version of markdown.
-final String version = '2.0.0';
+final String version = '2.0.1-dev';

pkgs/markdown/pubspec.yaml

diff --git a/pkgs/markdown/pubspec.yaml b/pkgs/markdown/pubspec.yaml
index 4ffb7db..16f0197 100644
--- a/pkgs/markdown/pubspec.yaml
+++ b/pkgs/markdown/pubspec.yaml
@@ -1,5 +1,5 @@
 name: markdown
-version: 2.0.0
+version: 2.0.1-dev
 author: Dart Team <misc@dartlang.org>
 description: A library for converting markdown to HTML.
 homepage: https://github.com/dart-lang/markdown
@@ -15,6 +15,8 @@
   charcode: '^1.1.0'
 
 dev_dependencies:
+  build_runner: ^0.8.2
+  build_web_compilers: ^0.4.0
   collection: '^1.2.0'
   expected_output: '^1.1.0'
   html: '>=0.12.2 <0.14.0'