Spring-ai Add Mistral AI documentation.

After the merge of https://github.com/spring-projects/spring-ai/pull/369 add * Mistral AI Chat client docs under: https://github.com/spring-projects/spring-ai/tree/main/spring-ai-docs/src/main/antora/modules/ROOT/pages/api/clients * Mistral Ai Embedding docs under: https://github.com/spring-projects/spring-ai/tree/main/spring-ai-docs/src/main/antora/modules/ROOT/pages/api/embeddings * Add a mistral chat and embedding items in the catalog: https://github.com/spring-projects/spring-ai/blob/main/spring-ai-docs/src/main/antora/modules/ROOT/nav.adoc

Comment From: tzolov

Resolved by 31d6194d9debb079ee3c3e30ee4d15abfa7c4db1 and aa55a96c9587f5bd87f480586b0fed92360a7f32