Add Makefile, package.json, and initial configuration for VitePress and Slidev integration

- Introduced a Makefile for streamlined commands related to building, running, and managing presentations.
- Created package.json to define project metadata, dependencies, and scripts for development and testing.
- Added .gitignore entries to exclude build artifacts and temporary files from version control.
- Included playwright.config.mjs for end-to-end testing setup with Playwright.
- Added README.md for project documentation, outlining setup instructions and development guidelines.

.gitignore

@@ -1 +1,14 @@
+# Slidev peut laisser un index.html à côté de slides.md (dev) — ne pas versionner
+slides/**/index.html
+
+node_modules/
+dist/
+dist-*/
+artifacts/
+portal/.vitepress/cache/
 .DS_Store
+*.log
+test-results/
+playwright-report/
+blob-report/
+playwright/.cache/