Default description for merge requests created from multiple commits
### Description
Merge requests created from multiple commits have empty default description.
### Proposal
A good description could look like this:
```
* commit subject 1
Commit description 1
* commit subject 2
Commit description 2
...
```
The practice of creating an MR from a single commit at a time doesn't fit all use cases, so it would be nice to support this as well.
issue