implemented chat archive

app/pubspec.yaml

@@ -29,8 +29,11 @@ dependencies:
   html: ^0.15.4
   http: ^1.2.1
   logger: ^2.2.0
+  markdown: ^7.2.2
   mime: ^1.0.5
   package_info_plus: ^8.0.0
+  path: ^1.9.0
+  path_provider: ^2.1.3
   riverpod: ^2.5.1
   riverpod_annotation: ^2.3.5
   rxdart: ^0.27.7
@@ -42,6 +45,7 @@ dependencies:
   universal_io: ^2.2.2
   uri_to_file: ^1.0.0
   url_launcher: ^6.2.5
+  watcher: ^1.1.0
 
 dev_dependencies:
   build_runner: ^2.4.9