Can we explicitly add a python3 supported code language.

[s-retlaw]

Is your feature request related to a problem? Please describe.
I have a system where I would like to be able to show a python 2.x version and a python 3.x version of a code sample.
They are installed as python and python3 on my system. I would like to add python3 as an option to execute code.

Describe the solution you'd like
Keep python to call whatever is mapped to python but also add python3 to allow the use of systems with both versions installed and mapped to the 2 options.

Describe alternatives you've considered
I can create a bash file work around but it would be nice to support it directly

Additional context
I have multiple systems (Linux and Mac) that have python running python 2.x and python3 running python 3.x simultaneously.

[vext01]

Related to this, I'm porting slides to OpenBSD and I'm looking at the interpreter dispatch code for code blocks.

On OpenBSD some interpreters (e.g. ruby) are always suffixed with a version number. I can patch that away, but it would be nice if the user could somehow provide their own command to use to evaluate the code block with?

Something like:

!!!awk -f blah.awk
input for awk

(I didn't think hard about !!!, there may be a better prefix)

[vext01]

Or maybe the languages can be configured via a config file?

[maaslalani]

Hey @vext01, I do want to support custom languages: #122

@s-retlaw Happy to accept a PR for python3 as well!

[vext01]

For now I've just patched the python block to invoke python3. OpenBSD has almost killed python2 support across the board.