rename to “Framework”; new Getting started tutorial

[mbostock]

This…

• Renames “the Observable CLI” to “Observable Framework”
• Rewrites the Getting started tutorial, including a dedicated section for Early Access
• Moves the project structure docs from Getting started to Routing
• Tweaks the home page copy
• Improves the default home page for observable create projects
• Prompts the user for a project title during observable create
• Fixes Creating a project at ~/path/to/file creates a folder literally named "~" #635
• Fixes We sometimes briefly see empty files when watching #157

This does not…

• Repoint links from cli.observablehq.com to observablehq.com/framework
• Rename the package from @observablehq/cli to @observablehq/framework
• Rename the project from @observablehq/cli to @observablehq/framework

These latter changes will follow later.

[mythmon]

The new tutorial seems like a good level of depth to me.

One issue I had while reading this is that the screenshots that include VSCode are a little hard to make sense of. I think that's mostly because I'm still using an oldschool 1x display. Maybe we could make those full width on screens with less pixels?

[mythmon]

For me, neither Alt-B nor Ctrl-B work in Chrome or Firefox on Linux or Windows. Super-B works in Chrome on Linux, but nowhere else. Hotkeys are hard :(

[mbostock]

I increased the max-width of the figures to 960px. You can right-click and open them in a new window too, if needed, but I think that’s as good as it’ll get.

[mythmon]

The increased max width on the image helps, thanks.