added Zarr gsoc proposal

[decryptofy]

Hi

Thanks that you have chosen to apply for a NumFOCUS project. You can use pull
requests on this repository to work on a draft of your proposal before the
student application period begins to get early feedback.

Before you open a pull request with a draft of your proposal please make sure
that you have contacted your organization beforehand. Some organization prefer
if you communicate on their preferred channel (email/irc) and are more likely to
give you feedback then. On the README we list the preferred contact
information of every organization and project idea.

best NumFOCUS GSoC Admins

[henrykironde]

Please update the README file links too and also fill out the spreadsheet we sent through group mailing list.

[MSanKeys963]

@henrykironde, please refer to the updated PR here: #454.
Feel free to close this PR.

Also, I haven't received the link for the spreadsheet. Can you please check and send it again?
Thanks!