Description of the Issue

Just like VS Code and Atom and some other editors, Notepad++ can also give ability to open folder as workspace, and better to provide this when running from command line.
Noticed it when trying to put an enhancement to Github Desktop project in this PR

Expected Behavior

There can be an argument like "-openAsWorkspace". When running notepad++ with this argument, it should open given folder as workspace.

C:\Program Files (x86)\Notepad++>"notepad++.exe" -openAsWorkspace "C:\newfolder"

Actual Behavior

It opens every file recursively. Especially when opening a software project solution folder, it warns about opening thousands of files.