fix(trng): Clarify documentation with a warning

epicardium/epicardium.h

@@ -1935,6 +1935,13 @@ API_ISR(EPIC_INT_RTC_ALARM, epic_isr_rtc_alarm);
  * Use :c:func:`epic_csprng_read` for cryptographically safe random
  * numbers instead.
  *
+ * .. warning::
+ *
+ *    The exact behaviour of the TRNG is not well understood. Its
+ *    distribution and other parameters are unknown. Only use this
+ *    function if you really want the unmodified values from the
+ *    hardware TRNG to experiment with it.
+ *
  * :param uint8_t * dest: Destination buffer
  * :param size: Number of bytes to read.
  * :return: `0` on success or a negative value if an error occured. Possible