var guidance

[Keboo]

Currently there is not guidance in the docs around var. With C# 9, this also somewhat expands to target-typed new expressions as well.

Previously the only written guidance was in Tom's blog.
We believe there should be some additional guidance provided here as well:

Both of the following should be put in a "Variables" section under "Coding"

• CONSIDER using var any time that the initialization of the variable clearly shows what the variable will contain.
• CONSIDER using target-typed new expressions any time that the instance clearly shows its type.