New version: Manifolds v0.9.20

[JuliaRegistrator]

• Registering package: Manifolds
• Repository: https://github.com/JuliaManifolds/Manifolds.jl
• Created by: @kellertuer
• Version: v0.9.20
• Commit: 676b0f5d0751f4899bec67a0a81b7f313e1f6db7
• Reviewed by: @kellertuer
• Reference: JuliaManifolds/Manifolds.jl@676b0f5#commitcomment-143260829
• Description: Manifolds.jl provides a library of manifolds aiming for an easy-to-use and fast implementation.
• Release notes:

### Added

* implemented parallel transport on the Grassmann manifold with respect to Stiefel representation

### Changed

* since now all exp/log/parallel transport are available for all representations of `Grassmann`,
  these are now also set as defaults, since they are more exact.

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