Monospace Gmail Plaintext extension for Chrome

gmail_monospace_plaintext.css

/* Message body and compose interface */
.ii, .Ak, .editable {
    font-family: monospace !important;
    font-size: 100% !important;
}

manifest.json

{
    "manifest_version": 2,

    "name": "Monospace Gmail Plaintext",
    "version": "1.0",
    "description": "This extension makes plantext emails in Gmail to be typeset with monospace font",
    "author": "ilammy",

    "content_scripts":
    [
        {
            "matches": [ "https://mail.google.com/*" ],
            "css": [ "gmail_monospace_plaintext.css" ]
        }
    ]
}