more type-annotations

[earloc]

With the work done in #15, we got a first impression how type-annotations can benefit the generated code. But there´s room for more, continuing work from #6 :

most of them should be implemented easily:

• [ ] integrals

  • [ ] sbyte
  • [ ] byte
  • [x] short
  • [ ] ushort
  • [x] int
  • [ ] uint
  • [x] long
  • [ ] ulong

  ---

  • [ ] nint
  • [ ] nuint

• [ ] floating-points

  • [x] float
  • [x] double
  • [x] decimal

• [ ] chars

These here might be a bit more challenging getting right

• [x] bools
• [ ] Enums
• [x] DateTimes
• [x] DateTimeOffsets
• [x] DateOnlys
• [x] TimeOnlys

[earloc]

marked some types as done, as of #255 arriving soon