Provide Installer for Windows

[nikku]

We dropped distributing the Windows installer via https://github.com/camunda/camunda-modeler/commit/5aec4b681e6e78489c7b509c514ccc2559a7e988, as it is erases the installation directory during update, effectively removing all configured plugins / element template (https://github.com/camunda/camunda-modeler/issues/867).

Tasks

• [ ] Re-enable installer by reverting https://github.com/camunda/camunda-modeler/commit/5aec4b681e6e78489c7b509c514ccc2559a7e988
• [ ] Extend the installer to not remove custom files, added by the user, cf. https://github.com/electron-userland/electron-builder/issues/3201#issuecomment-409868207
• [ ] Automatically wire .bpmn, .dmn and .form extensions with the installation

Hint

Unfortunately the creator of electron-builder indicated that this is a non-feature for him (cf. https://github.com/electron-userland/electron-builder/issues/3201). Because of that we must implement the stuff ourselves using the extension points electron-builder provides.

[nikku]

Without an installer we'll not be able to wire file associations (https://github.com/camunda/camunda-modeler/issues/3352#issuecomment-1386725842).