Add EasyCLA instructions (#1314)

* Add EasyCLA instructions

Signed-off-by: Brian Warner <[email protected]>

* Improvements to EasyCLA instructions

Signed-off-by: Brian Warner <[email protected]>

Author: brianwarner

README.md

@@ -325,6 +325,16 @@ $ yarn start
 Open
 [localhost:3000/localDev.html?endpoint=https://api.graph.cool/simple/v1/swapi](http://localhost:3000/localDev.html?endpoint=https://api.graph.cool/simple/v1/swapi) for local development!
 
+### Contributing to this project
+
+TThis repository is managed by EasyCLA. Project participants must sign the free ([GraphQL Specification Membership agreement](https://preview-spec-membership.graphql.org) before making a contribution. You only need to do this one time, and it can be signed by [individual contributors](http://individual-spec-membership.graphql.org/) or their [employers](http://corporate-spec-membership.graphql.org/).
+
+To initiate the signature process please open a PR against this repo. The EasyCLA bot will block the merge if we still need a membership agreement from you.
+
+You can find [detailed information here](https://github.com/graphql/graphql-wg/tree/main/membership). If you have issues, please email [[email protected]](mailto:[email protected]).
+
+If your company benefits from GraphQL and you would like to provide essential financial support for the systems and people that power our community, please also consider membership in the [GraphQL Foundation](https://foundation.graphql.org/join).
+
 ## Custom Theme
 
 From `[email protected]` on you can provide a `codeTheme` property to the React Component to customize your color theme.