ts2dart crashes on first run, please set reasonable defaults for sdk environment

[truedat101]

Following the suggested change in #1 , I've changed the sdk min to the recommended. My own system on 3.16 dart language, I cannot compile without encountering #1 . The correct approach is to set a reasonable min SDK in the pubspec.yaml files, and document the potential for an issue in the top level README.md.

The solution in this case requires inline support to built in, either through the experimental flag, or implicitly by default.