Add README and screenshot

README.md

@@ -0,0 +1,36 @@
+# BetterTRN
+An educational computer emulator!
+___
+
+![screenshot](https://raw.githubusercontent.com/tatokis/bettertrn/master/screenshot.png)
+
+Originally developed at NTUA.
+
+Unfortunately, the original software was really slow, with many bugs, and practically unusable on Linux despite being written in Java.
+BetterTRN is a complete implementation of the TRN+ computer from scratch, using the cross platform Qt framework, with many, many improvements.
+
+## Installation
+
+### Windows
+Download the latest [win32 release archive](https://github.com/tatokis/bettertrn/releases/latest) and extract it somewhere. Then run `bettertrn.exe`.
+
+### Linux
+Build from source. Either use Qt Creator, or run the following commands.
+Instructions are for Ubuntu, but should apply to all distros with the appropriate package manager command
+
+```
+sudo apt install build-essential git qt5-default
+git clone https://github.com/tatokis/bettertrn
+cd bettertrn
+qmake && make -j4
+./bettertrn
+```
+
+### macOS
+Either install the official Qt package and open up the project in Qt Creator, or use homebrew with qmake + make
+
+## Documentation and examples
+Can be found inside the docs and examples folders.
+
+## License
+Licensed under GNU GPLv3 or (at your option) any later version. See LICENSE.