[jsx-no-target-blank] Doesn't fail when external url is put in a variable

[kenearley]

This is considered an error:

var Hello = <a target='_blank' href="http://example.com/"></a>

This is not an error:

var url = "http://example.com/"
var Hello = <a target='_blank' href={ url }></a>

Since the vulnerability we are trying to prevent is user generated links to malicious sites, this rule seems too lax.

[kenearley]

Oops! This seems to be a duplicate of #1737