Make hostname unique per board.

(Attempt to) make the hostname unique per board, by using the last
four chars of the unique ID (flash chip ID) as a suffix.

Fixes #167

enviro/__init__.py

@@ -153,7 +153,7 @@ def stop_activity_led():
 print("    -  --  ---- -----=--==--===  hey enviro, let's go!  ===--==--=----- ----  --  -     ")
 print("")
 
-def reconnect_wifi(ssid, password, country):
+def reconnect_wifi(ssid, password, country, hostname=None):
   import time
   import network
   import math
@@ -165,6 +165,11 @@ def reconnect_wifi(ssid, password, country):
   # Set country
   rp2.country(country)
 
+  # Set hostname
+  if hostname is None:
+      hostname = f"EnviroW-{helpers.uid()[-4:]}"
+  network.hostname(hostname)
+
   # Reference: https://datasheets.raspberrypi.com/picow/connecting-to-the-internet-with-pico-w.pdf
   CYW43_LINK_DOWN = 0
   CYW43_LINK_JOIN = 1