Awesome bar/landing page redesign

[betatim]

BinderHub's current landing page is a form with a lot of fields, dropdown menus and options. You can do "everything" with it but it isn't very friendly for newcomers and hard to discover what the different options do/when you should use them.

In contrast there is https://addons.mozilla.org/en-US/firefox/addon/open-with-binder/ which let's you click a button when you are on any kind of page that could be launched on mybinder.org. It will try its best to figure out how to construct the URL to visit (basically what to put in which part of the form).

This issue is about designing and then implementing what we are calling "the awesome bar". Ideally the BinderHub landing page would only have a single text box into which people paste the URL of the repository/notebook/thing they want to run on Binder and it figures everything else out.

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We could get a start on the "parse URL and do magic" part by reusing the code from the Firefox extension.

The Binder team doesn't have a huge amount of experience with frontend development so this is a call for help to those who have experience with UX/UI design and those who have skills on the web dev front.

There are a few constraints we should stick with: the colour scheme should fit with what we have now, we aren't looking for a radical colour/design change. The tech stack should somehow fit the following description: "modern JS, react based, opinionated, simple to maintain and deploy as part of a tornado app".

See #351 for previous discussions on the awesome bar.

See #777 for an existing suggestion and plan in terms of "tech stack" (its ideas have support so probably wise to stick with it or at least not deviate massively).

[alexmorley]

Tagging @cassiecardiff in case she's interested in mocking up a UI or two.

[nuest]

At the Binder/Jupyter meeting in Oslo the last days, we discussed what "screens" a new BinderHub UI might entail, extending on the idea of the awesomebar, and here are the notes: https://hackmd.io/teR1MefxSjW9mLJTLSSCjw

[betatim]

There are more thoughts (in particular on the API binderhub has to expose) in #351