fix: export region should support es6 class and block openings

[ccarpita]

Currently, the following syntax results in an error on the closing
brace:

export default {
} // <-- error here

export default class Modules extends Base {
} // <-- error here

This patch adds jsBlock to be included in a jsExportContainer region
so that region matching will continue to the end of the class or block.

[ccarpita]

This commit fixes issue GH-256

[qstrahl]

Let's give this a shot

[goatslacker]

I remember this breaking certain things, lets give it a whirl now.