Update web implementation to use platform interface.

just_audio_web/pubspec.lock

@@ -0,0 +1,70 @@
+# Generated by pub
+# See https://dart.dev/tools/pub/glossary#lockfile
+packages:
+  characters:
+    dependency: transitive
+    description:
+      name: characters
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.0"
+  collection:
+    dependency: transitive
+    description:
+      name: collection
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.14.13"
+  flutter:
+    dependency: "direct main"
+    description: flutter
+    source: sdk
+    version: "0.0.0"
+  flutter_web_plugins:
+    dependency: "direct main"
+    description: flutter
+    source: sdk
+    version: "0.0.0"
+  just_audio_platform_interface:
+    dependency: "direct main"
+    description:
+      path: "../just_audio_platform_interface"
+      relative: true
+    source: path
+    version: "0.0.1"
+  meta:
+    dependency: "direct main"
+    description:
+      name: meta
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.8"
+  plugin_platform_interface:
+    dependency: transitive
+    description:
+      name: plugin_platform_interface
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.2"
+  sky_engine:
+    dependency: transitive
+    description: flutter
+    source: sdk
+    version: "0.0.99"
+  typed_data:
+    dependency: transitive
+    description:
+      name: typed_data
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.2.0"
+  vector_math:
+    dependency: transitive
+    description:
+      name: vector_math
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.8"
+sdks:
+  dart: ">=2.9.0-14.0.dev <3.0.0"
+  flutter: ">=1.12.13+hotfix.5"