Add "context-menu" DOM event to <webview>

lib/browser/guest-view-manager.js

@@ -18,6 +18,7 @@ const supportedWebViewEvents = [
   'did-get-redirect-request',
   'dom-ready',
   'console-message',
+  'context-menu',
   'devtools-opened',
   'devtools-closed',
   'devtools-focused',

lib/renderer/web-view/guest-view-internal.js

@@ -16,6 +16,7 @@ const WEB_VIEW_EVENTS = {
   'did-get-redirect-request': ['oldURL', 'newURL', 'isMainFrame'],
   'dom-ready': [],
   'console-message': ['level', 'message', 'line', 'sourceId'],
+  'context-menu': ['params'],
   'devtools-opened': [],
   'devtools-closed': [],
   'devtools-focused': [],