Add sources to existing Data Sources page

[katjost]

Please add a list or table (developer's choice) of the source articles to this page, underneath the first line of text
https://balancertestsite.com/data-sources

Please ensure:

• Article names are links to the article
• Article links open in a new browser tab
• Article name is really the name of the article, not necessarily what someone uploaded it as (let me know if extracting article names needs to be a separate ticket)

[katjost]

Tai will add a source_title column