Compiler: Enable breakpoints within ST blocks

[FunctionPoint]

Blocks are the ST implementation of JS anonymous functions.
Currently is it is not possible to set breakpoints inside blocks in ST code.
In TypeScript, that also uses source mapping, this does seem possible.
Find out how to make it work for ST files too.

[FunctionPoint]

This seems to be an issue with VSCode / SourceMaps.
Made an issue here with a use-case that works and one that does not work:
microsoft/vscode-js-debug#2250