feat: made initial changes for valkey docs

[Kemi-Elizabeth]

Valkey draft

Still a work in progress but adjusted first half of redis add services page to make the new valkey draft add services page. still need more info from remi to complete.

Why

Closes #4361

What's changed

Added new Valkey add-services page.

Where are changes

Add services section. New valkey page. Still a work in progress so content needs to be verified and expanded. Other pages need to be created too.

Updates are for:

• platform (sites/platform templates)
• upsun (sites/upsun templates)

[github-actions]

Your Platform.sh environment has successfully deployed. 🚀

See the changed pages:

Platform.sh docs

• https://4361-create-new-for-6itwbqa-ucq44jg6ofare.eu-5.platformsh.site/add-services/valkey.html
• https://4361-create-new-for-6itwbqa-ucq44jg6ofare.eu-5.platformsh.site/guides/drupal/valkey.html
• https://4361-create-new-for-6itwbqa-ucq44jg6ofare.eu-5.platformsh.site/add-services/redis.html
• https://4361-create-new-for-6itwbqa-ucq44jg6ofare.eu-5.platformsh.site/guides/drupal/redis.html

Upsun docs

• https://docs.upsun.com.4361-create-new-for-6itwbqa-ucq44jg6ofare.eu-5.platformsh.site/add-services/valkey.html
• https://docs.upsun.com.4361-create-new-for-6itwbqa-ucq44jg6ofare.eu-5.platformsh.site/add-services/redis.html
• https://docs.upsun.com.4361-create-new-for-6itwbqa-ucq44jg6ofare.eu-5.platformsh.site/get-started/stacks/laravel/setup-redis.html