Added Multi-Factor Authentication

[chesspro13]

Added A tab in the options menu to enable Multi-Factor Authentication (MFA) in the form of Time-Based One Time Passwords (TOTP) for a layer of security.

Addresses issue #68

[eliandoran]

Hi,

I'm surprised to see such a feature come so soon to Trilium Next, can't wait to test it.

In the mean time, could you please have a look at the whitespace changes (e.g. two spaces where there used to be four)? I would like them removed in order to maintain consistency.

[chesspro13]

I'm canceling this pull request. I found a bug in the login causing MFA to be enabled before a secret is set. I'll update the white space as well.

Can you create a MFA branch that I can push to without pushing to the develop branch?

Edit: No bug, just didn't have the correct branch checked out.

[eliandoran]

@chesspro13 , I've assigned you to the dev team, you should now be able to push your own branches.
Nevertheless, we still require PRs so that we can review them. When you create the PR from a branch from our fork, please make sure the target repository is TriliumNext, since GitHub can accidentally put the original one from zadam instead.