Elsa 2 Dashboard - API enhancement on Designer WebComponent(s) to facilitate integration as a third party tools

As a developper, I would like to integrate the designer and other part of the Web Components inside my application.

A discussion around __Embedding designer already exist__ #800 but this issue is more to provide and think about what api/properties could be useful to expose for allowing interaction with outside (React/Angular/Blazor, etc..)

Here is the props I see for the beginning about ElsaWorkflowDefinitionEditorScreen Component :

- [ ] Expose the WorkflowDefinition or at least Workflow high level props (like name, description , variables, customprops... without Activities and Connections)
- [ ] Expose the API to manipulate specifics props --> maybe it could be better to allow to GET/SET variables for example without exposing all the WorkflowDefinition
- [x] Be able to handle with a middleware or something like that the HTTP Call --> the idea here could be to call an external api to get some info before saving/after load to fill custom data into the WorkflowDefinition) , maybe this could already be done by changing the serverUrl and use some sort of proxy by we're not working on the FrontEnd with this kind of solution)

feel free to add some ideas to help on usecase possibility and allow dev to prioritize this as best