create what's new for April

[BillWagner]

Run the app to create "what's new" for April.

[gewarren]

LG. A few comments:

• There will be some updates to https://docs.microsoft.com/en-us/dotnet/core/project-sdk/msbuild-props worth mentioning (does the tool go off PRs in the April project?).
• Should we add redirects for the deleted pages each month?
• I also added some breaking changes for .NET Core 1.0 and 3.0 and .NET 5 (Scott Addie did too).

[BillWagner]

@gewarren @scottaddie

• There will be some updates to https://docs.microsoft.com/en-us/dotnet/core/project-sdk/msbuild-props worth mentioning (does the tool go off PRs in the April project?).
  The code goes off the project / sprint dates. So, those should show up next month.
• Should we add redirects for the deleted pages each month?
  So far, we've decided against it. This is another use case for folder level redirects, where any outdated link could redirect to the "what's new" landing page. As it exists now, this becomes another tax on the global redirection file.
• I also added some breaking changes for .NET Core 1.0 and 3.0 and .NET 5 (Scott Addie did too).
  Can you and Scott make PRs to add those by hand? Then, they are highlighted, and I can figure out why the tool missed them and fix it.

[gewarren]

Can you and Scott make PRs to add those by hand? Then, they are highlighted, and I can figure out why the tool missed them and fix it.

If What's new for April is for work completed in March, then these should just show up next month.