Allow defining package description and compat data in config file

[MarkTiedemann]

// in jsr.json or deno.json
{
  "description": "...",
  "compat": {
    "browsers": true,
    "deno": true,
    "node": true,
    ...
  }
}

[marvinhagemeister]

Looks like we have an issue about defining the compatibility data in jsr.json already https://github.com/jsr-io/jsr/issues/147

[lucacasonato]

Closing as duplicate