Prepare for PetitParser 7.0.0

Author: renggli

pubspec.yaml

@@ -21,9 +21,9 @@ dependencies:
   http: ^1.2.0
   meta: ^1.16.0
   more: ^4.5.0
-  petitparser: ^6.0.0
+  petitparser: ^7.0.0
   web: ^1.1.0
-  xml: ^6.5.0
+  xml: ^7.0.0
 dev_dependencies:
   build_runner: ^2.4.0
   build_web_compilers: ^4.1.0
@@ -32,4 +32,6 @@ dev_dependencies:
 
 dependency_overrides:
   petitparser:
-    path: ../petitparser
+    git: https://github.com/petitparser/dart-petitparser.git
+  xml:
+    git: https://github.com/renggli/dart-xml.git