[ZEPPELIN-2191] Helium package should be able to import css

[1ambda]

What is this PR for?

Helium package should be able to import css. For example,

• Someone want to create spell using jsoneditor (https://github.com/josdejong/jsoneditor/blob/master/docs/usage.md). In this case, he/she should import css

import'jsoneditor/dist/jsoneditor.min.css'/** here */importJSONEditorfrom'jsoneditor/dist/jsoneditor.min.js'

This PR is written based on #2071, so the duplicated commit will be dropped. Please review the commit 505c7db only.

What type of PR is it?

[Improvement]

Todos

• - denote required packages in package.json
• - setup webpack.config.js

What is the Jira issue?

ZEPPELIN-2191

How should this be tested?

Should be able to bundle zeppelin-json-spell

Screenshots (if appropriate)

NONE

Questions:

• Does the licenses files need update? - NO
• Is there breaking changes for older versions? - NO
• Does this needs documentation? - NO

[1ambda]

CI failed, but irrelevant.

• build profile: https://travis-ci.org/1ambda/zeppelin/builds/206002571
• failed log1: https://s3.amazonaws.com/archive.travis-ci.org/jobs/206002573/log.txt
• failed log2: https://s3.amazonaws.com/archive.travis-ci.org/jobs/206002574/log.txt

[AhyoungRyu]

Tested 505c7db commit only with your package, and it works well as expected.

(zeppelin-json-spell: super nice package!)

[1ambda]

@AhyoungRyu Thanks for cool review 😃

[AhyoungRyu]

LGTM 👍

[AhyoungRyu]

Merge into master if there are no more comments!

[1ambda]

Rebased to resolve conflict.