Add i18n and a11y ability to the state machine designer

## 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.

Start with the state machine designer README.md, especially its explanation of the diagram-js module system, and review the refactor_designer branch mentioned in the issue. Define and integrate translation and accessibility capabilities for the designer, with the result working across the relevant designer UI.

Written by the indexing model from the issue text.