Add i18n and a11y ability to the state machine designer

[ptyin]

Why you need it?

Currently, we need to develop an available state machine designer as quickly as possible. However, in a long term perspective, We should integrate International and accessibility capabilities to the designer.

How it could be?

You can use module system in diagram-js to create a Translation module to achieve that. If you dont know what is a module system, plz refer to state machine designer README.md

Other related information

Please merge related PR to the refactor_designer branch.