[Kobo] Add preliminary Kobo Aura H2O2 definition (#3372)

Cf. ongoing discussion in KSM8 thread: https://www.mobileread.com/forums/showthread.php?p=3596020#post3596020

frontend/device/kobo/device.lua

@@ -96,6 +96,16 @@ local KoboPhoenix = Kobo:new{
     viewport = Geom:new{x=0, y=0, w=758, h=1012},
 }
 
+-- Kobo Aura H2O2:
+local KoboSnow = Kobo:new{
+    model = "Kobo_snow",
+    hasFrontlight = yes,
+    touch_phoenix_protocol = true,
+    display_dpi = 265,
+    -- the bezel covers the top 11 pixels:
+    viewport = Geom:new{x=0, y=11, w=1080, h=1429},
+}
+
 -- Kobo Aura second edition:
 local KoboStar = Kobo:new{
     model = "Kobo_star",
@@ -534,6 +544,8 @@ elseif codename == "star" then
     return KoboStar
 elseif codename == "daylight" then
     return KoboDaylight
+elseif codename == "snow" then
+    return KoboSnow
 else
     error("unrecognized Kobo model "..codename)
 end