Added note about missing maintainers to readme

[s1hofmann]

I added a note about missing maintainers for various reasons:

• No commits / merges for over half a year
• No proper release (0.6.0 only supports macOS and is therefore broken
• No recent releases since end of 2019
• No support for recent node versions
• Lots of unresolved issues

[dchicchon]

Just wanted to add to this thread, are there any alternatives to RobotJS that provide similar features?

[s1hofmann]

Shameless plug: I’m maintaining https://github.com/nut-tree/nut.js which is built on top of my fork of robotjs.
It evolved separately, solves quite a few issues and provides additional features like a plugin architecture to use addons for e.g. on-screen image search

[dchicchon]

Thanks! Actually I looked up alternatives and it's one of the first ones I found that works out of the box 👍🏼