[REF] convenience commands for testing against a local kernel

[stevejpurves]

Problems this addresses:

• Getting local development to work with a local kernel was not discoverable from the docs
• switching to local changes required a code change to development.html, easy to commit in error

This PR aims to make it easier to chose to test against a local kernel without needing to change the code and improve discoverability.

Changes

• moved single development.html to a folder and split to local.html and binder.html to cover the two cases
• split out css to avoid repetition
• added a note to the contributors guide
• ensure previous npm run develop command works as before
• added a npm run develop:local command to bring up the local page
• added some instructions on how to start kernel on the local page

[choldgraf]

This seems good to me 👍 thanks for updating the documentation as well, agree it is much easier to run this locally and iterate more quickly

can you get the lint test passing before merging though?

[moorepants]

LGTM too!

[stevejpurves]

thanks, I suggest we rebase this after getting #424 in which resolves the package-lock.json issue.

[stevejpurves]

@moorepants @choldgraf The lint issue is ongoing but being dealt with see #426 , it would be great to get this PR in ahead of Monday if possible :D

[moorepants]

@TimStewartJ, It would be great if you try out this PR. You can get some review practice in and help out @stevejpurves. I can also try this out too.

[TimStewartJ]

Yep, tried it out and it looks good to me as well!

Edit with more relevant information:

I've messed around with both of the new HTML files and I agree that it allows for a much cleaner quick development environment. Appending and removing -disabled on the thebe configs in the old development.html got old pretty quick.

The new package scripts are a nice touch and well appreciated as well. I've tried them out and they work great.

[stevejpurves]

This one is now green ✅ on the lint stage too.
I resolved the conflicts with the updated master branch and this is ready to merge! 🥳