Add native Run button support

[LightingBulb]

Currently, the extension lacks the runnables.scm configuration, meaning Zed's native visual Run button does not appear for standalone scripts or main functions outside of rigid project structures. Adding a Tree-sitter query to detect main :: IO () would allow the native play button to appear.

[sectore]

Following in a runnables.scm will detect main functions (very similar to what go extension does):

(declarations
  [
    (function name: (variable) @run) @_
    (bind name: (variable) @run) @_
  ]
  (#eq? @run "main")
  (#set! tag haskell-build)
  (#set! tag haskell-run))

Works well. I have just tested it locally in a Haskell project.

However, there are still questions:

1. How to avoid a false positive check? There might be a case where a main function is also used for running tests.

2. Where and how to define tasks to run needed commands? An extension might provide a "default" tasks.json. But in this case: Does it include commands to run cabal OR stack OR both? I would prefer cabal only. Users still can override such default tasks.json in a global or project settings of Zed.

   Something like that:

   [
     {
       "label": "cabal build",
       "command": "cabal build",
       "tags": ["haskell-build"]
     },
     {
       "label": "cabal run",
       "command": "cabal run",
       "tags": ["haskell-run"]
     }
   ]

[sectore]

However, there are still questions:

1. Can be ignored (as other extension it does)
2. Stack/Cabal auto-detection done in Add native Run button support #38

All solved then.