Setup Wiki.js for new wiki.

[Amar Takhar]

As we transition off of Trac we'll need a new wiki to replace ​https://devel.rtems.org/

​https://js.wiki/ offers the best situation for us for several reasons:

• It uses Markdown as it's main language
• It can replicate itself to a Git repository making easy branching or local copies of the wiki. It can directly interface with GitLab.
• We can, in the future build a PDF using Sphinx from the Git repository.
• It supports OATH so we can log in using our local GitLab instance.
• Has instant search capabilities.

Moving to a purely Sphinx based system is too heavyweight for developer documentation as an open source project we need to have a strong focus on lowering the barrier to contributions. Documentation lags behind everything else as it we shouldn't be making it more difficult to contribute.

There is one downside to this as anyone who wants to modify the wiki will need to have their local GitLab account approved whereas Trac currently is automatic right after applying.