Display of numerical values

[martin-henz]

In Python §1, Python integers are represented by JS big ints, and Python floating point numbers by JS numbers (doubles). The display of values in the REPL should reflect this: We should append ".0" to JS numbers when we print them, in case JS stringify makes them look like integers:

print(100.000)

should show

100.0

in the REPL.

This should be doable with the new multi-language support in js-slang, see https://github.com/source-academy/js-slang/pull/1651/files.