Enhance sourecFileMap documentation (#4844)
Enhance sourecFileMap documentation (#4844)

The documentation for `sourceFileMap` was not very through. This tries to make things more clear.
gregg-miskelly/omnisharp-vscode,OmniSharp/omnisharp-vscode,gregg-miskelly/omnisharp-vscode,gregg-miskelly/omnisharp-vscode,OmniSharp/omnisharp-vscode,OmniSharp/omnisharp-vscode,OmniSharp/omnisharp-vscode,gregg-miskelly/omnisharp-vscode,OmniSharp/omnisharp-vscode