Update README.md

Author: rafi16jan

README.md

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+MicroPython.js
+==============
+
+MicroPython transmuted into Javascript (WASM) by Emscripten.
+
+Running with Node.js
+--------------------
+
+```javascript
+var mp_js = require('micropython');
+
+mp_js.init(64 * 1024);
+mp_js.do_str("print('hello world')\n");
+```
+
+Running with Webpack
+-----------------
+TODO
+
+API
+---
+
+The following functions have been exposed to javascript.
+
+```
+init(stack_size)
+```
+
+Initialize MicroPython with the given stack size in bytes. This must be
+called before attempting to interact with MicroPython.
+
+```
+do_str(code)
+```
+
+Execute the input code. `code` must be a `string`.
+
+```
+init_repl()
+```
+
+Initialize MicroPython repl. Must be called before entering characters into
+the repl.
+
+```
+process_char(char)
+```
+
+Input character into MicroPython repl. `char` must be of type `number`. This 
+will execute MicroPython code when necessary.