Add `CODEOWNERS` file to allow doc team to be notified of when GCP bucket is updated

[alallema]

Description
For each release on this repository, a new public bucket is published on GCP, and the address to this bucket must be updated in the documentation.
To ensure that the documentation team is aware of this change, a CODEOWNERSfile should be added.

Disadvantage
The granularity of the CODEOWNERS feature is at the file level, so, unfortunately, the @meilisearch/docs-team will be notified for every modification on the main file on this repo.

To do

• Give write access to @meilisearch/docs-team
• Create CODEOWNERS file at the root