Partial translation to French (2/3) of docs/index.md
Merge branch 'master' of github.com:ocaml/ocaml.org into docs-index.fr.md
Merge branch 'master' into docs-index.fr.md
Put back breadcrumbs
Merge pull request #422 from lefessan/docs-index.fr.md

Partial translation to French (2/3) of docs/index.md