Specifies the projects to have metadata extracted. There are several approaches to extract language metadata.

1. From a supported project file or project file list. Supported project file extensions include .csproj, .vbproj, .sln.
2. From a supported source code file or source code file list. Supported source code file extensions include .cs and .vb. Files can be combined using , as seperator and search pattern.
3. From docfx.json file.

If the argument is not specified, docfx.exe will try reading docfx.json under current directory.

public IEnumerable<FilePath> Projects { get; set; }