Generated API references from OpenAPI file

[curquiza]

⚠️ Needs meilisearch/meilisearch#6145 to be merged

Docs

• Use openAPI file to generate API reference
• Split API reference Overview page into sub pages, still uder API reference group
• Github -> GitHub
• Add missing code sample for /indexes/uid/fields route

Internal tooling and CIs

• Improve Post deployment CI to trigger and generate OpenAPI files (+ creation of the scripts)
• Add CI to check code samples in open API file (+ creation of the scripts)
• Add PR template to ensure we do not miss steps related to code samples
• Add scripts to npm commands, and so use npm run instead of directly the scripts in CIs