fix: set document title

[barmac]

Closes #4376

Proposed Changes

This PR replaces the main process code used for the window title with an HTML <title> tag. The content is hard-coded as "Camunda Modeler" in contrast to the old solution where we added "(dev)" for dev mode, but this piece of information is already represented in the bottom-right "what's new" button. The main advantage of the current solution is that the a11y tools won't report missing title anymore.

Checklist

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• [x] Brief textual description of the changes present
• [ ] Visual demo attached
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[github-actions[bot]]

This Pull Request targets develop branch, but contains fix commits.

Consider targeting main instead.