Do not fail if GUI port is already occupied

[shadowusr]

Contribution

• [ ] I'd be willing to implement this feature (contributing guide)

Describe the user story

Often users work with multiple projects simultaneously. Currently, when trying to launch html-reporter in GUI mode, it will fail with an error that port is already taken.

Describe the solution you'd like

We should find free port automatically, like it's usually done in other tool and write a helpful message to user.

Describe the drawbacks of your solution

No response

Describe alternatives you've considered

No response