Create new Intro screen

[johnarban]

This PR creates a new intro screen for showing where things are on the main view

[patudom]

Even with the shorter text, this was still happening on my phone.

My above commit is an attempt to push the "close" icon outside the overlay in the corner. I'm not crazy about it because the white x box on blue sky doesn't have quite enough contrast. Black on sky has a bit more contrast, but it felt less associated with the overlay because of the white outline. This is what it looks like on my phone:

@johnarban, let me know what you think. We can come up with another solution if you don't like this.

[patudom]

Ok, one more commit above. This slightly edits the text, and I think the text for the right-hand div looks better right-justified.

Only issue now is that the bottom arrows don't really point at quite the right thing, and the overlay box covers up a lot of the time controls. I don't know how we would set this up to work correctly on all form factors, so if it looks good on your phones, I'm inclined to call it good enough since my phone is usually the wonky one.

[johnarban]

i pushed a commit to try to better adjust sizes on the smaller screens