bump version to 1.2.0 in pubspec.yaml and pubspec.lock

Author: warioddly

example/pubspec.lock

@@ -104,7 +104,7 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "1.1.2"
+    version: "1.2.0"
   integration_test:
     dependency: "direct dev"
     description: flutter

pubspec.yaml

@@ -4,7 +4,7 @@ repository: "https://github.com/warioddly/graphify"
 documentation: "https://echarts.apache.org/en/option.html#title"
 issue_tracker: "https://github.com/warioddly/graphify/issues"
 
-version: 1.3.0
+version: 1.2.0
 
 environment:
   sdk: '>=3.2.3 <4.0.0'