Add clearer "about us" and "contribute" section

- Modify `resources/public/md/about.en.md` and
- add section "about us" and "contribute" with
  link to documentation

Signed-off-by: Louis Vigneras <louis.vigneras@code.gouv.fr>
src/codegouvfr/core.cljs: Remove links to deps and libs from home
Rename /public to /sources
src/codegouvfr/core.cljs: Don't display stars
Fix domain names and typos
fix bug: Remove trailing slash
src/codegouvfr/core.cljs: Update footer
Update to use dsfr 1.11.2
Update copyright years
src/codegouvfr/core.cljs: Minor UI enhancements
src/codegouvfr/i18n.cljs: Shorten strings
src/codegouvfr/core.cljs: Use the ugly X instead of the nice bird
Bump dsfr version
README.md: Be more explicit about what this repo is about

Thanks to Adrien Di Pasquale for suggesting this.
Fix permissions
src/codegouvfr/core.cljs: Fix double quotes escaping for csv

Thanks to Marc Chance for reporting this.
resources/public/index.html: Add link to Mastodon account
deps.edn: Fix repository URL
deps.edn: Bump version
deps.edn: Bump dependencies