Cleanup and documentation updates:

• minor updates to release docs (MRG: minor updates to release docs #3695)
• small docs fixes and updates (MRG: small docs fixes and updates #3681)

Developer updates:

• release core 0.21.0 (MRG: release core 0.21.0 #3712)

Dependabot updates:

• Build(deps): Bump camino from 1.1.9 to 1.1.10 (Build(deps): Bump camino from 1.1.9 to 1.1.10 #3669)
• Build(deps): Bump cfg-if from 1.0.0 to 1.0.1 (Build(deps): Bump cfg-if from 1.0.0 to 1.0.1 #3689)
• Build(deps): Bump conda-incubator/setup-miniconda from 3.1.1 to 3.2.0 (Build(deps): Bump conda-incubator/setup-miniconda from 3.1.1 to 3.2.0 #3676)
• Build(deps): Bump getset from 0.1.5 to 0.1.6 (Build(deps): Bump getset from 0.1.5 to 0.1.6 #3700)
• Build(deps): Bump prefix-dev/setup-pixi from 0.8.8 to 0.8.10 (Build(deps): Bump prefix-dev/setup-pixi from 0.8.8 to 0.8.10 #3688)
• Build(deps): Bump proptest from 1.6.0 to 1.7.0 (Build(deps): Bump proptest from 1.6.0 to 1.7.0 #3674)
• Build(deps): Bump pypa/cibuildwheel from 2.23.3 to 3.0.0 (Build(deps): Bump pypa/cibuildwheel from 2.23.3 to 3.0.0 #3687)
• Build(deps): Bump roaring from 0.10.12 to 0.11.0 (Build(deps): Bump roaring from 0.10.12 to 0.11.0 #3702)
• Build(deps): Update maturin requirement from <1.9.0,>=1 to >=1,<1.10.0 (Build(deps): Update maturin requirement from <1.9.0,>=1 to >=1,<1.10.0 #3699)
• Build(deps): Update pytest requirement from <8.4.0,>=6.2.4 to >=6.2.4,<8.5.0 (Build(deps): Update pytest requirement from <8.4.0,>=6.2.4 to >=6.2.4,<8.5.0 #3670)
• EXP: Revert "Build(deps): Bump pypa/cibuildwheel from 2.23.3 to 3.0.0 (Build(deps): Bump pypa/cibuildwheel from 2.23.3 to 3.0.0 #3687) (EXP: Revert "Build(deps): Bump pypa/cibuildwheel from 2.23.3 to 3.0.0 (#3687) #3691)
• [pre-commit.ci] pre-commit autoupdate ([pre-commit.ci] pre-commit autoupdate #3668)
• [pre-commit.ci] pre-commit autoupdate ([pre-commit.ci] pre-commit autoupdate #3673)
• [pre-commit.ci] pre-commit autoupdate ([pre-commit.ci] pre-commit autoupdate #3698)