Add "Link supplementary reads" type functionality

[cmdcolin]

Requested by user on gitter. we have a demo of this for a poster a long time ago, but it was never merged to main branch (old demo https://s3.amazonaws.com/jbrowse.org/code/jb2/beta/skbr3_demo/index.html?config=test_data%2Fconfig_demo.json&session=share-4e68d7667f204ee4dfaf01279ee488275686147d4c93c86a80fb2994ad6c43c6&password=c17703bc1fc0d1c7508bc1af8cf42892)

this is an IGV'ism

[cmdcolin]

Example of how to do this "today" with the breakpoint split view. The links are more spidery since each connected read is not laid out simultaneously but it helps a bit