Release gpustat-web v0.3.0

Fix regression on event_loop in aiohttp 3.8 (#19)

app.loop is deprecated from since 3.5.0 in favor of global event_loop,
but this somehow stopped working with aiohttp 3.8.x (which was fine
in aiohttp 3.7.x or earlier).

With this change, aiohttp works fine with all versions I could test
(aiohttp 3.6.3, 3.7.4, 3.8.1, and 4.0.0.a1).