Add a README.md on the script file format

src/scripted_input/README.md

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+# ScriptedInput
+
+This is a system for supplying button/pad/touch input to the emulator from a file, rather than user input.
+
+It also supports saving screenshots of the game, so they can be compared with past behaviour.
+
+This allows us to create reproducable test cases that utilize real games, so we can test the behaviour citra.
+
+## Script File Format
+
+Example
+```bash
+30 # first line isn't allowed buttons
+10 a # get through the first menu
+10
+10 start # get through the second menu
+10
+10 [200,150] # Touch the button
+10
+screenshot # screenshot of second menu fading out
+```
+
+Each line starts with a number, this is how many frames to run. It is then followed by a space separated list of buttons.
+
+Optionally a line maybe a have a comment, started with a `#` character, everything after that is ignored.
+
+If a line starts with `screenshot` then a screenshot will be saved at that time, the file is named `{framenumber}.bmp` and saved in the current working directory.
+
+**THE FOLLOWING ARE NOT YET IMPLEMENTED**
+
+Touch screen input can be denoted with `[100,100]`, where the numbers are the pixel location of the touch (0-320, 0-240).
+
+Circle pad input can be denoted with `(-1,1)`, where the numbers are the joystick location (from -1 to 1). If not specified, the circle pad will be at (0,0).
+
+C-stick input can be denoted with `{1,-1}`, where the numbers are the joystick location (from -1 to 1). If not specified, the C-stick will be at (0,0).