Add more promenient App Passwords instruction where needed

[notpushkin]

Right now, Gmail sign in looks like this:

It's easy to skip this and causes . Some ideas:

• Add brief step-by-step instructions instead of just linking to the guide
• Replace the password label with “App Password (what is this?)”

This goes for all OAuth e-mail providers.

[kosssi]

In my opinion the screen "Connect an email account" is useless, instead we should see an email field. According to the provider then we will display specific information.

[notpushkin]

@kosssi Yeah, it makes sense, and I've implemented it some time ago, but this got lost after an update (#42). We should reintroduce that at some point!

[exprez135]

I agree! I left that out because I intended to look into OAuth stuff. I will look to reintroduce that :)