~vince/poc_libgit2sharp

Update reference to submodule

Signed-off-by: Scherb Vincent <scherb.vincent@gmail.com>
Add submodule libgit2sharp on master

Signed-off-by: Scherb Vincent <scherb.vincent@gmail.com>
Update LibGit2Sharp version to preview

In the issues for the library is indicated that there are problems with
.Net 5 with those problems solved in the preview version of the NuGet.

With this fix the program runs without an error.

Signed-off-by: Scherb Vincent <scherb.vincent@gmail.com>
Add simple check for the library

Checking if a Repository is valid will use the library to check if that
path contains a valid git repository.

Signed-off-by: Scherb Vincent <scherb.vincent@gmail.com>
Add LibGit2Sharp NuGet

Signed-off-by: Scherb Vincent <scherb.vincent@gmail.com>
Add initial project files

Signed-off-by: Scherb Vincent <scherb.vincent@gmail.com>