String index access isn't changed to zero-based in the generated python code

[vf42]

Consider a sample F# function:

let test1 (s: string) : bool =
    if s.Length < 3 then false else s[3] = 'A'

When compiled to Python with Fable, I get the following output:

def test1(s: str) -> bool:
    if len(s) < 3:
        return False

    else: 
        return s[3] == "A"

Which results in incorrect behavior since in python list and string indices are zero-based.

Expected behavior: index access on the last line to be updated as s[2]

$ dotnet fable --version
4.16.0

[vf42]

Realized this belongs in https://github.com/fable-compiler/Fable/issues