Better shell detection

[mxsdev]

Currently, to detect the capabilities of a shell, we use the name of the executable (bash, sh, ksh, pwsh, etc). This is not really fool-proof since shells can be (and often are) aliased to other shells.

I looked into it, and unfortunately there does not seem to be a unified way to determine this information. Looks like every shell has a distinct way of indicating what kind of shell it is :(