OSD Forum website needs to have the Code of Conduct added

https://www.osdforum.org/ I believe we decided that all events needed a visible link to the Code of Conduct (https://events.eclipse.org/code-of-conduct/). I just noticed the OSDForum event doesn't have this link, so we need to add it.

For an example, see the SAM IoT website: https://events.eclipse.org/2020/sam-iot/

Thanks.