README Update
README Update

Updating Contributing guidelines to make note of the `env: custom` option so that a Sync Engine in a local environment may be accessed on an alternate IP.

Also APIRoot must contain quotes around the URL otherwise a config validation will be thrown.

Signed-off-by: Julien Chinapen <d38fdb681fe5bf81e04233607133e4ddc01116e7@shogun.io>

nylas/nylas-mail,nylas-mail-lives/nylas-mail,simonft/nylas-mail,nirmit/nylas-mail,simonft/nylas-mail,nylas-mail-lives/nylas-mail,simonft/nylas-mail,nirmit/nylas-mail,nylas-mail-lives/nylas-mail,nylas/nylas-mail,nylas/nylas-mail,nylas/nylas-mail,nylas-mail-lives/nylas-mail,nylas/nylas-mail,nirmit/nylas-mail,simonft/nylas-mail,simonft/nylas-mail,nylas-mail-lives/nylas-mail,nirmit/nylas-mail,nirmit/nylas-mail