Move Wiki from wiki.eclipse.org to Github

[lcaron]

wiki.eclipse.org is deprecated and will disappear in the future (see https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/wikis/Wiki-shutdown-plan)

Our wiki has to been migrated (see https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/wikis/Wiki-Move-FAQ)

[merks]

I noticed readme (which is outdated) also refers to this page which is completely outdated too:

https://wiki.eclipse.org/Nebula/Builds

This also has some outdated things:

https://github.com/eclipse/nebula/blob/master/CONTRIBUTING.MD

There should be no references to https://git.eclipse.org/r/plugins/gitiles/nebula/org.eclipse.nebula or anything git.eclipse.org.

[merks]

I've updated/correct the readme significantly but it still has a reference to this which should be updated as part of the wiki migration:

https://wiki.eclipse.org/Nebula/Contributions/New_Widgets

[lcaron]

Thank you for your comments @merks ;)