Add link to data publishing self assessment guide

[kuang5]

PURR ticket: https://purr.purdue.edu/support/ticket/2755

We want to display a link to the data publishing self assessment guide before the button "Start a new publication" as attached, where the guide can help users understand what is required in their dataset submission. The guide is prepared by our data curator Sara and she will create an article and save the article URL to the link.

Test procedure

1. Fill the URL to the self assessment guide article in field data_publishing_self_assessment_guide on publication component configuration user interface on PURR admin, then save it.
2. Login on PURR and visit any of your project. Click tab "Project Datasets", you should see a button "Data Publishing Self Assessment Guide" shows before "Start a new publication". When clicking the button "Data Publishing Self Assessment Guide", it is going to take you to the article about the guide.
3. When URL is not set in the field data_publishing_self_assessment_guide on publication component configuration, the button won't show up in front of the "Start a new publication".

I have tested the changes on dev PURR and it works there.

Jerry