Properly collect commit messages

See the code near this line: https://github.com/ForNeVeR/Fenrir/blob/14987a6eb698db416986bbb16ba40140107ae1ca/Fenrir.Application/Ui/CommitsViewModel.fs#L25

Also, look for the number of this issue in the project code base.

Currently, we collect the commit message from the commit body by splitting the first several metadata lines.

We should provide some better way of doing this, for the user convenience (in case there are more metadata lines etc.).

Start with Fenrir.Application/Ui/CommitsViewModel.fs at line 25, then search the project codebase for issue 88. Review how commit messages are currently collected by splitting metadata lines; done means providing a more reliable, user-convenient way to handle messages when additional metadata lines are present.

Written by the indexing model from the issue text.