Consider showing UTC offset in tooltip for datetimes

Say I have

import pandas as pd
dfa = pd.DataFrame(
    {
        "datetime": ["2020-10-25T01:30"] * 2,
        "price": [40, 50],
    }
)
dfa['datetime'] = pd.to_datetime(dfa['datetime']).dt.tz_localize('Europe/London', ambiguous=[True, False])
dfa

                   datetime  price
0 2020-10-25 01:30:00+01:00     40
1 2020-10-25 01:30:00+00:00     50

and I plot

px.scatter(dfa, x="datetime", y="price")

then I get

Notice how the two points are stacked one on top of each other, even though they are actually 1 hour apart

If Plotly's design decision for time zones is to display the local datetime, then I think this makes perfect sense, nice one 👍 However, I think the tooltip should give enough information to distinguish the two points, whereas currently, they both show:

datetime=Oct 25, 2020, 01:30

I would expect the bottom one to show datetime=Oct 25, 2020, 01:30 +01:00 and the top one to show datetime=Oct 25, 2020, 01:30 +00:00

先執行 issue 中的 Python 重現程式，並檢查 Plotly 如何在 hover tooltip 中格式化 datetime 值。完成的標準是：透過顯示 UTC offset，兩個有歧義的 Europe/London datetime 仍能彼此區分，並為此範例加入 coverage。