[librsvg] (21 commits) ...Merge branch 'devel-docs' into 'main'

[Marge Bot <marge-bot src gnome org>]

Summary of changes:

  c9e5976... CI: install Sphinx in the opensuse-stable container
  9484ec4... Start a Sphinx skeleton for the developer's documentation
  f37e3fe... Outline the developer's documentation
  9257a5e... Reorder a bit
  1516263... References
  aca4225... Update the roadmap
  423b5ed... devel-docs/contributing.rst: Start a list of projects that 
  020705d... typo fix
  ab36b3e... Start a chapter with "Librsvg as a product" to describe the
  4e5fc89... Skeleton chapter for the CI
  a0a3032... Link the contributing chapter
  9bb2a22... Some more things for the outline.
  4d23fb1... Install sphinx-rtd-theme
  3560338... Use the sphinx_rtd_theme
  27889c7... contributing.rst: Fix markup
  cba35b6... Finish describing "librsvg as a product"
  3cd6f91... Add a devel-docs job to the CI
  60fb6c4... Markup fixes
  1c2eaf7... Chapter on how to set up a development environment
  31af1bb... Bump the base tag for the container image
  6539b77... Merge branch 'devel-docs' into 'main'