New features:
- `experimental.XRayTransform`: add `.diagnostic_plot()` to help verify specified geometries are correct.
- Add *weighted* XRT.
Bug fixes:
- ufuncs: correct operator shapes in functional API.
- `ArgShiftRule()`: correct shift parameter (in docs.)
- XRT tutorial: correct parallel beam specifiers. (Wasn't always parallel previously.)
- XRT: protect against out-of-bound reads, which would randomly cause crashes.