Add explicit permissions section[^1] to workflows. This is a security
best practice because by default workflows run with extended set
of permissions[^2] (except from `on: pull_request` from external forks[^3].
By specifying any permission explicitly all others are set to none. By using
the principle of least privilege the damage a compromised workflow can do
(because of an injection[^4] or compromised third party tool or action) is
restricted. It is recommended to have most strict permissions on the top
level[^5] and grant write permissions on job level[^6] on a case by case
basis.