Add CLA link

[skeggse]

New contributors may wish to review the CLA prior to working on a pull request. Currently, the only obvious way to view the CLA is to open a pull request.

[jsf-clabot]

All committers have signed the CLA.

[boneskull]

in the future I'd recommend adding [ci skip] to the commit message to avoid builds on a documentation change

[coveralls]

Coverage increased (+0.04%) to 89.072% when pulling 0855783 on skeggse:patch-2 into e39a867 on mochajs:master.

[boneskull]

thanks again

[ScottFreeCode]

in the future I'd recommend adding [ci skip] to the commit message to avoid builds on a documentation change

Is this mentioned in our CONTRIBUTING and PR TEMPLATE guides? If not we should add it too!