Add extensions to groovy highlighting

Summary:
BUG: 403072

Added two extensions for groovy.xml syntax highlight.

• *.gvy which is another option for *.groovy
• Jenkinsfile which uses the same groovy syntax (which also fixes mentioned bug)

Reviewers: Framework: Syntax Highlighting, dhaumann

Reviewed By: Framework: Syntax Highlighting, dhaumann

Subscribers: dhaumann, kwrite-devel, kde-frameworks-devel

Tags: Framework: Syntax Highlighting, Kate, Frameworks

Differential Revision: https://phabricator.kde.org/D19974