merge homebrew support

[ott2]

This is now worth considering. I added a minimalist formula, some fixes to the original cask, expanded the readme, and fixed an unrelated syntax error in one of the install scripts which blocks the formula build.

• This perhaps needs testing on Linux.
• The JDK dependency seems really messy but should be at least mentioned somehow in the documentation and ideally declared in both the cask and formula.
• I would ideally also like to use stack and a GHC installed by brew instead of running a binary to install stack, but that will probably have to wait until Conjure moves to Haskell 9.x since the 8.x releases in brew aren't being maintained.
• See also the todo and caveats in the readme.