Populate wiki homepage

**Is your feature request related to a problem? Please describe.**
The wiki home page is completely empty. This makes the MoDiBo project unwelcoming.

**Describe the solution you'd like**
Create a wiki home page for the `.github` repository, which details the following:

- [ ] What MoDiBo is
- [ ] What MoDiBo does
- [ ] Who MoDiBo is for
- [ ] How to install and setup MoDiBo
- [ ] How to install MoDiBo plugins and where to find them
- [ ] How can users contribute
- [ ] Brief introductions and links to other pages on the wiki

Start with the empty MoDiBo wiki homepage and use the checklist in the issue as the completion criteria. Document what MoDiBo is, its users and setup, plugin installation and discovery, contribution guidance, and links to other wiki pages; the payload names no files or tests to run.

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