feat(pycardium): add trng module

Documentation/pycardium/trng.rst

+.. py:module:: trng
+
+``trng`` - True Random Number Generator
+=======================================
+
+.. py:function:: trng.getrandombytes(n)
+
+   Returns a bytearray of random bytes from the TRNG.
+
+   :param int n:  Amount of bytes to return.
+