[feat] On the windows app allow override of default browser for weblinks

## Describe the feature

I would prefer to use a different browser to the Windows default browser for web links in Forward Email. I don't want to replace the default browser system wide for Windows.

This may be a niche use case - using Forward Email and a different browser for personal use (whilst on a 'work' machine), where I still have to use outlook/etc. that needs to use edge for auto-sign in to sharepoint/etc.

## Checklist

- [x] I have searched through GitHub issues for similar issues.
- [x] I have completely read through the README and documentation.