feat(chained_prs): add description on chained PRs

[danielRep]

PR Description

This PR introduces to the contributing guidelines a description on when and why to use a chain of PRs.

Type of change

• feat: introduces a new functionality
  • Logical unit: <contributing.rst>

Checklist:

• The changes follows the documentation guidelines described in here.
• The changes generate no new warnings when building the project. If so, I have justified above.
• I have run the CI checkers before submitting the PR to avoid unnecessary runs of the workflow.

[josecm]

This part of the documentation needs to differentiate between two topics in development:

• Chained PRs themselves that are a way to issue multiple PRs, on which one PRs depends on the other.
• WIP branches development process, which is a way to, for a large contribution, provide separate PRs that are reviews and merged separately for a temporary WIP branch, and that will later be merged to main based on a separate PR.

As an alternative, you could issue separate PRs for each one.

[danielRep]

This part of the documentation needs to differentiate between two topics in development:

• Chained PRs themselves that are a way to issue multiple PRs, on which one PRs depends on the other.
• WIP branches development process, which is a way to, for a large contribution, provide separate PRs that are reviews and merged separately for a temporary WIP branch, and that will later be merged to main based on a separate PR.

As an alternative, you could issue separate PRs for each one.

I just self-contained this PR on the description of chain of PRs and created a new one #73 to explain the process of splitting large PRs.

[DavidMCerdeira]

Please rebase the branch with main

The merge-base changed after approval.

[danielRep]

Please rebase the branch with main

Done.