Adding new workflow to check if framework branch and PR exist

[juanangp]

Added new workflow for automatic merging of framework PR when a framework branch matches and a PR exist:

• Check if any framework branch matches current branch for merging
• In case a branch matches it check if a PR in the framework exist
• Workflow will fail in case a matching framework branch exist and there is no associated PR
• When the current PR is merged, the associated framework PR should be also merged
• Access tokens for the merge are taken from the repository

Contributes to rest-for-physics/framework#250

Related to rest-for-physics/framework#259