Added: LDM notes for April 13th, 2020

[MgSam]

https://github.com/dotnet/csharplang/blob/master/meetings/2020/LDM-2020-04-13.md

Didn't see an issue for this so I'll open this one.

[SingleAccretion]

I like the decision to only allow init for properties a lot. To me this makes the feature much more straightforward and simple (When should I use init fields? Are those fields "better" than readonly? How are they different anyway?) but still very powerful.

Btw, for people who are interested, init has also recently been discussed by the (runtime & BCL) team (see here).

[MgSam]

I for one am already starting to write TODO comments in my codebase where I want to change properties to init after C# 9.0. 😃