v5.1.0-rc4 - Fourth pre-release

What's Changed

• chore(docs): document HTML custom templates by @jeertmans in #357
• [pre-commit.ci] pre-commit autoupdate by @pre-commit-ci in #358
• chore(deps): bump pdm-project/setup-pdm from 3 to 4 by @dependabot in #360
• chore(deps): bump ssciwr/setup-mesa-dist-win from 1 to 2 by @dependabot in #361
• chore(deps): make Qt backend optional by @jeertmans in #350

Full Changelog: v5.1.0-rc3...v5.1.0-rc4