docs: Add python block usage examples

[icweaver]

Following up from the discussion here, added some brief usage examples for calling blocks of Python code interactively

[cjdoris]

Looks great thanks. CI failures are a separate issue I'm dealing with.

Only suggestion is could you change the second example to show using inputs as well as multiple outputs? Perhaps something along the lines of

@pyexec (x=3) => """
    y = x + 1
    z = x - 1
    """ => (y, z)

which also shows that you can name the inputs and outputs as well.

[icweaver]

Sounds good, just added and included a type conversion example too. I also updated the indenting to match your style

[cjdoris]

Nice thank you - docs improvements are always appreciated.