build: make the AngularJS plugin an optional dependency

This plugin should not force the installation of AngularJS.
If it is installed we'll provide completion items,
if it isn't nothing will be added to the completion popup.

Author: lppedd

src/main/resources/META-INF/angular_js.xml

@@ -0,0 +1,6 @@
+<idea-plugin>
+  <extensions defaultExtensionNs="com.github.lppedd.idea-conventional-commit">
+    <commitTypeProvider implementation="com.github.lppedd.cc.angular2.Angular2CommitTypeProvider" />
+    <commitScopeProvider implementation="com.github.lppedd.cc.angular2.Angular2CommitScopeProvider" />
+  </extensions>
+</idea-plugin>

src/main/resources/META-INF/plugin.xml

@@ -9,11 +9,6 @@
   </vendor>
 
   <depends>com.intellij.modules.platform</depends>
-  <depends>AngularJS</depends>
   <depends>com.github.lppedd.idea-conventional-commit</depends>
-
-  <extensions defaultExtensionNs="com.github.lppedd.idea-conventional-commit">
-    <commitTypeProvider implementation="com.github.lppedd.cc.angular2.Angular2CommitTypeProvider" />
-    <commitScopeProvider implementation="com.github.lppedd.cc.angular2.Angular2CommitScopeProvider" />
-  </extensions>
+  <depends optional="true" config-file="angular_js.xml">AngularJS</depends>
 </idea-plugin>