Support writing text to the host's clipboard

[ace-dent]

Describe the feature
It would be useful to be able to send text to the host OS clipboard.

To Reproduce
Steps to reproduce the behavior:

1. As per PICO-8: printh('test','@clip').
2. Command seems to execute, but no text is written to clipboard.

Expected behavior
Feature not implemented.

Software (please complete the following information):

• OS: [macOS
• Version: v0.1.0b

[ace-dent]

Seems to be supported with set_clipboard("foo") ...?
But doesn't support extended character set; e.g. set_clipboard(chr(128)) silently fails to update clipboard.

[ace-dent]

Re-tested with release v0.1.0g on macOS. Problem still exists.