docs(readme): Rewrite presentation and tagline to clarify platform focus

[ebouchut]

Update the project's tagline and presentation. Remove any mention of hands-on exercises. These are planned for v2.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.59%. Comparing base (2e0723f) to head (d9d67e5).
⚠️ Report is 2 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff            @@
##                dev     #125   +/-   ##
=========================================
  Coverage     81.59%   81.59%           
  Complexity      201      201           
=========================================
  Files            38       38           
  Lines           864      864           
  Branches         53       53           
=========================================
  Hits            705      705           
  Misses          125      125           
  Partials         34       34           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.