Enforce writing commit message bodies

### Description

Frequently contributors do not write a commit message body, and it becomes difficult to see the rationale or benefit of the change, or the reason why a particular approach was chosen.

### Impact analysis

Not writing a commit message body makes it difficult to understand past changes when navigating the git history, and any relevant exchange may remain only on the GitHub comments.

### Expected behavior

We should enforce e.g. through a pre-commit hook writing a commit message body.

### Actual behavior

Commit message bodies can be empty.

### Versions

`master`.

### Environment

Any.

### Additional Information

Although we cannot ensure self-contained, complete message bodies, this will at least avoid empty commit message bodies.