Set the amend and supersede relations in the meta section of the ADR

[asiermarques]

In order to improve the integration and automation, as the ADR writer, I need the ADR relations are specified in the meta section of the ADR file

In order to be able to choose to improve the integration and automation, as the ADR writer, I need to have a config parameter to activate the creation of meta relation variables in the ADR files

Acceptance criteria:

Given a file without meta sections and the relations_in_meta config variable is true
When I create a new ADR with a relation
Then the meta section is added with the relation variable in it

Given a file with a meta section and the relations_in_meta config variable is true
When I create a new ADR with a relation
Then the meta section is updated with the relation variable in it

Given a file with a meta section and the relations_in_meta config variable is false
When I create a new ADR with a relation
Then the meta section is not created either updated