Documentation improvements

[MarcAstr0]

Description

Style improvements to the documentation and some revised texts to better understand some concepts.

Changes

• Apply a consistent style to admonitions.
• Edit section on read model query join keys (introduced in Read Models projections by ReadModel query #1469)

Checks

• Project Builds
• Project passes tests and checks
• Updated documentation accordingly

[what-the-diff]

PR Summary

• Added a new read model class
  The website/docs/03_architecture/06_read-model.mdx file now includes information about a new class named CarPurchasesReadModel. This class contains different properties such as id, carModel, carOwner, and offers, for organizing car purchasing data.

• Updated the read model documentation
  The read model documentation has received several updates for clarification and completeness. These additions include the behavior when a read model doesn't match a query, the use of read models for data validation, and more detailed instructions on read model filtering.

• Improvements to query documentation
  An update to the website/docs/03_architecture/08_queries.mdx file reflects that query subscriptions are currently not available.

• Updated GraphQL documentation
  Several updates have been made to the website/docs/06_graphql.md document. Notes on the limitations of selecting fields from objects within arrays, the usage of the select function for skipping read model migrations, and the use of read models for data validations have been added. Additionally, information on querying entities for up-to-date states, sorting, and pagination limitations has been incorporated.

• Inserted note on EventStream functionality on Azure
  The document website/docs/10_going-deeper/azure-scale.mdx now mentions that EventStream functionality is only available for the Azure provider.

• Amended sensor health documentation
  The website/docs/10_going-deeper/health/sensor-health.md file now clarifies that details will be included only if enabled and that rockets sensors are currently available only for the Azure provider.

• Added warning and examples for removing events
  The website/docs/10_going-deeper/remove-events.mdx file now includes a warning about the experimental nature of the remove event functionality and its limited support, as well as an example of deleting a ReadModel, and a note about the irreversibility of changes from deleting events.

• Updated contributing guidelines
  For the website/docs/12_contributing.md the project now contains a note about referencing related closed issues when creating a new issue, helping to keep context and history linked.