blocks style self post reflector

[StoneCypher]

Closely related to #180, basically another arg for implicit load target

Instead of https://fsl.tools/viewer/?u=this-%3Eis-%3Ea-%3Emachine; , do https://fsl.tools/viewer/?gh=stonecypher/foo_repo/machines/bar.fsl

Needs a secondary argument whether to render

1. the graph (default),
2. the source highlighted,
3. 1/2 side by side,
4. an editor

This is superior in some cases to in-URL machines because these can point at a repo which is updated over time

possibly on .gallery #155