Sparse-ir

[Diff since v0.11.0](https://github.com/SpM-lab/SparseIR.jl/compare/v0.11.0...v0.12.0)


**Closed issues:**
- Perfomance of evaluating uhat (6)

[Diff since v0.10.0](https://github.com/SpM-lab/SparseIR.jl/compare/v0.10.0...v0.11.0)


**Closed issues:**
- Speeding up evaluating overlap (3)
- Improve perfomance of fit (5)

This release adds more documentation.

We have decided to rename the `irbasis3` to `sparse-ir` for consistency with the Julia package.