ProtonMail improvements

[Neustradamus]

Dear @lbuchs,

I have a problem to create a PR: Pull request creation failed. Validation failed: must be a collaborator

The source of changes is here:

• https://github.com/lbuchs/WebAuthn/compare/master...ProtonMail:WebAuthn:master

Done by @wussler from @ProtonMail team.

Thanks in advance.