Added: LDM Notes for May 13, 2019

[jcouv]

https://github.com/dotnet/csharplang/blob/master/meetings/2019/LDM-2019-05-13.md

Agenda:
Close on desired rules for warning suppressions and #nullable interacting

[Joe4evr]

Oh nice, so #nullable enable annotations is a solution to the declaration-site of the DTO problem.

Now I hope that the next update to Nullable will add something that makes the compiler warn at construction-sites (#2328).