Make inspect command work on current expression, add inspect-prompt

[yuhan0]

Credit goes to @alexander-yakushev in #613 :)

• The commits are consistent with our contribution guidelines
• You've added tests to cover your change(s)
• All tests are passing
• The new code is not generating reflection warnings
• You've updated the README (if adding/changing middleware)

[yuhan0]

Oh, but now the commit message and changelog doesn't line up with the actual change, not sure if I can edit that without overwriting authorship

[bbatsov]

@yuhan0 Just add a second commit that changes this.

[yuhan0]

It turns out I could squash the previous commit without overwriting authorship info, learnt something new about Git :)

[bbatsov]

Great! I'll push a new snapshot out.

[alexander-yakushev]

🥳
Thanks, @yuhan0 and @bbatsov!