Cherab 1.6.0 release

[Mateasek]

Tasks and steps before releasing Cherab 1.6.0:

Pull Requests

• finish code review & merge PR Improve regularisation documentation and add ADMT demo #427 (@jacklovell, @Mateasek, @munechika-koyo, @skuba31 )
• finish code review & merge PR Add GaussianQuadrature2D #476 (@jacklovell, @Mateasek, @munechika-koyo, @skuba31 )
• finish code review & merge PR ✨ Introduce pixi for project management #489 (@jacklovell, @Mateasek, @munechika-koyo, @skuba31 )
• finish code review & merge PR Feature/generic dist #494 (@jacklovell, @Mateasek, @munechika-koyo, @skuba31 )

Build

• Automatic Conda-forge builds triggered by new (release) tag on Cherab repo (@munechika-koyo)
• Develop cibuildwheel workflow for automatically building all release wheels (@jacklovell)

Documentation

• Change documentation to encourage developers to use pixi package manager and recommend it as the primary development tool (@munechika-koyo)
• check documentation installation with conda (@munechika-koyo)

Release

• release Cherab 1.6.0 release candidate (@jacklovell)

Post-release

• update cherab-solps repository to require Cherab 1.6.0 (@Mateasek, @skuba31 )
• update cherab-JET repository to require Cherab 1.6.0 (@Mateasek, @skuba31 )
• update cherab-MAST repository to require Cherab 1.6.0 (@jacklovell )