try/catch/finally - explicit syntax documentation

[callendorph]

Can we please add an explicit description of the syntax in the try/catch/finally section.

For example - the docs don't suggest that the catch can be optional but it clearly can:

(venv) ➜  slm git:(jw/add-pkgdependency) stanza repl
stanza> try:
      >   println("asdf")
      > finally:
      >   println("qwer")
      > 
asdf
qwer
false