Issue #3512891: Connect pseudofield sources in diagram

Closes #3512891

• Config to enable/disable pseudofield edges in graph
• Rename JS to mermaid.js since it's only used for Mermaid
• Whew, getting Mermaid's Elk renderer to behave was fun, lol
• Move CDN libraries to imports (since it worked)
• Coding standards & tidy as you go
• Connect edges for pseudofield destination to source
• Add Mermaid front matter