docs: Add a new SDKs menu to the website

[thomaspoignant]

Description

Adding a new menu into the website to access directly to the different SDKs.

Checklist

• I have tested this code
• I have updated the documentation (README.md and /website/docs)
• I have followed the contributing guide

[netlify]

✅ Deploy Preview for go-feature-flag-doc-preview canceled.

Name	Link
🔨 Latest commit	92d8b95
🔍 Latest deploy log	https://app.netlify.com/projects/go-feature-flag-doc-preview/deploys/68f673e976b7ad000810f19c

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.76%. Comparing base (8909ed2) to head (92d8b95).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4107   +/-   ##
=======================================
  Coverage   83.76%   83.76%           
=======================================
  Files         139      139           
  Lines        6831     6831           
=======================================
  Hits         5722     5722           
+ Misses        899      898    -1     
- Partials      210      211    +1     

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud