✨(sdk) add sdk projects

It includes a consumer project which is simply a demo app. The sdk
project includes the first version of the SDK, with a light React
implementation. The first version lays down the foundations of
the iframe sdk framework. The npm package logic is also already
ready to be published.

src/sdk/library/CONTRIBUTING.md

@@ -0,0 +1,17 @@
+# Contributing
+
+## Release
+
+1. Run `npm run build`
+
+2. Update CHANGELOG.md according to the Major / Minor / Patch semver convention.
+
+3. Based on semver upgrade the package version in `package.json`.
+
+4. Commit the changes and create a PR named "🔖(release) version packages".
+
+5. Run `npx @changesets/cli publish`. It will publish the new version of the package to NPM and create a git tag.
+
+6. Run `git push origin tag @gouvfr-lasuite/visio-sdk@<VERSION>`
+
+7. Tell everyone 🎉 !