Improve documentation

Currently, there are some problems with documentation:

1. There is not nearly enough of it.
2. User documentation and development documentation is mixed.
3. Documentation is spread out over too many places. In many cases, there is duplication, instead of linking people to the correct place. These places are:
   3.1. The OpenRCT2 wiki
   3.2. docs.openrct2.io (not working since the move from .website to .io now fixed)
   3.3. openrct2.org No longer active
   3.4. openrct2.io (Getting Started) moved to docs.openrct2.io
   3.5. readme.md moved to wiki

Instead, the documentation should be reorganised as follows:

• 1. User documentation should go to docs.openrct2.io, which should also revert to RST/ReadTheDocs.
• 2. Technical documentation should stay on the OpenRCT2 wiki - for now at least.
• 3. Both should be vastly expanded.

Review the current documentation locations listed in the issue, especially docs.openrct2.io and the OpenRCT2 wiki, and compare them with the stated organization. The remaining work is to identify concrete documentation gaps and expand the appropriate user and technical documentation without duplicating content.】【。}