Provide userscript metadata that works

[chocolateboy]

The default userscript metadata doesn't work, and doesn't raise an error. Add a copy 'n' pasteable stanza that works so the library can be used without diving into the source code.

• GM_addStyle is needed for the default mode (iframe).
• GM_registerMenuCommand is needed for the suggested menuCommand: true option.
• GitHub should no longer be used as a CDN.
• GreasyFork requires 3rd party libraries served from GitHub-mirror CDNs to have either a commit hash or a tag. In the absence of any MonkeyConfig tags/releases, use the former.