feat: add "Accessible Label" setting

[aleclarson]

Description

Allow the user to set the aria-label attribute.

This is maybe a controversial feature, but it would be useful for post-processing that I'm doing on the generated output. 😅

Before merging

• tested locally and on preview environment (preview dev login: 0000)
• updated test cases document
• added tests
• if any new env variables are added, added them to .env file

[kof]

User can add aria-label to any instance, not sure why aria-label needs to become a system property.

[kof]

It would be nice to expose aria-label on all components where likelyhood of using it is high as initialProperties, so that user doesn't need to add it, its already visible

[TrySound]

Is it necessary for all components or only buttons and links which often have icons as content?

[TrySound]

So yes the best option is specifying aria-label where needed
https://github.com/webstudio-is/webstudio/blob/main/packages/sdk-components-react/src/button.ws.ts#L33

System props and core components are used to manage their behaviour with builder and cli instead of generic code generation.

[kof]

I meant adding it to initial only on components where users would be using aria label potentially, buttons, links and similar, I don't remember if we have it in initialProps in all of them, maybe its a non-issue.