* supports `--index` option
* add an option to drop selected stash after applying
* remove `Pop` context menu for stash
Signed-off-by: leo <longshuang@msn.cn>
* use `--pathspec-from-file=<FILE>` in `git add` command if git >= 2.25.0
* use `--pathspec-from-file=<FILE>` in `git stash push` command if git >= 2.26.0
* use `--staged` in `git stash push` command only if git >= 2.35.0
* remove dotnet-tool.json because the project does not rely on any dotnet tools.
* remove Directory.Build.props because the solution has only one project.
* move src/SourceGit to src. It's not needed to put all sources into a subfolder of src since there's only one project.
