CI: add pre-commit and validate actions and workflows schema

[noirbizarre]

This PRs:

• adds pre-commit to the repository (already enabled on pre-commit.ci) to:
  • lint actions and workflows using checkjsonschema
  • lint and format markdown using markdownlint (config added)
  • check typos using codespell
• add an .editorconfig to preconfigure editors supporting it
• fixes all lints and typos

It should avoid new typos to be submitted as well as non functionnal actions or workflows. It will also ensure minimal diffs and allow contributors to format using shared rules whatever the tool they use.