Create initial emulator and hello world demo

README.md

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+# Wipforth
+
+## Building and Running
+
+To run, first compile the WebAssembly module:
+
+```
+wat2wasm --enable-threads wipforth.wat
+```
+
+Then run the server:
+
+```
+python3 server.py
+```
+
+You should then be able to open <http://localhost:8080> in a browser
+and use the system from there.
+
+**NOTE**: The server is just a very simple instantiation of Python's
+built-in `http.server` that sets the cross-origin headers required for
+`SharedMemoryBuffer` use.  You could use any HTTP server that sets
+these headers.
+
+## Peripherals
+
+# Serial
+
+| Name   | Offset | Size / B | Access       |
+|--------|--------|----------|--------------|
+| TXBUF  | 0      | 32       | write        |
+| RXBUF  | 32     | 32       | read         |
+| TXDATA | 64     | 1        | atomic write |
+| TXHEAD | 65     | 1        | atomic read  |
+| TXTAIL | 66     | 1        | atomic write |
+| RXDATA | 67     | 1        | atomic read  |
+| RXHEAD | 68     | 1        | atomic write |
+| RXTAIL | 69     | 1        | atomic read  |
+
+For both sending (`TX`) and receiving (`RX`), there are four
+registers: `xBUF`, `xDATA`, `xHEAD` and `xTAIL`:
+
+- `xBUF` registers are 32-byte FIFO ring buffers used for data
+- The `xDATA` registers indicate whether data is available (0 for
+  data, FFh for no data)
+- The `xHEAD` and `xTAIL` registers specify the start and end of
+  data in the FIFO, `xHEAD` being the offset of the first byte of
+  data, and `xTAIL` being the offset of the first byte after the
+  data.