Action needed to release 0.5.0

• [x] doc contributors users
• [x] all issues with good metadata
• [x] link to rss for blog (issues/grafts)
• [x] doc all plugins with purl
• [x] update all plugins layout and data for purl

After update

• [x] update allowed signers && update plugins with purl
• [x] update pollen config with kind and blog
• [x] delete blog/index.md
• [x] change my email from gmail to gitroot
• [x] rss for blog
• [x] update toc article to link it (from relative to absolute)
• [x] add nbmaxbranchesbeforerejectinganonymous in repoConf.yml