Add Directives to Variable definitions

[stevan]

This is a small commit to add directives to variable definitions. This is something which is supported in the JS reference implementation and has been added into the spec working draft. Please let me know if there are any issues with the PR.

Thanks, Stevan

[facebook-github-bot]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. In order for us to review and merge your code, please sign up at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need the corporate CLA signed.

If you have received this in error or have any questions, please contact us at [email protected]. Thanks!

[facebook-github-bot]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Facebook open source project. Thanks!

[stevan]

Adding some links to supporting information here:

An older RFC to add support for it Now it is part of the current draft spec And it is supported in the reference implementation