forge fmt usage in zed

[sakulstra]

Configuring foundry fmt to be used in zed is slightly different to vscode.

Not sure if it makes sense to add an extra page for zed? Was considering to do a pr, but seems to be not so reasonable.
Perhaps could make sense to change the docs layout to formatting -> setup instructions for different editor opposed to the current vscode page.

In case anyone is looking for it, here is how you can configure foundry fmt in zed:

"format_on_save": "on"
  "languages": {
    "Solidity": {
      "formatter": {
        "external": {
          "command": "forge",
          "arguments": ["fmt", "--raw", "-"]
        }
      }
    }
  }