enable arbitrary formatting on x-axis and y-axis tick labels

Thanks for the awesome work on this project! It is incredibly useful!

I have a feature request. I work for a hedge fund and we want our plotly graphs to follow a standardized format. I am having a hard time through writing a generic formatting function that formats the x-axis and y-axis tick values.

For instance, if you wanted to set the tick axis to be bold and include a "x" at the end, you would need to do something like:

fig.update_layout(
    yaxis = dict(
        tickmode = 'array',
        tickvals = [1, 2, 3],
        ticktext = ["<b>1x</b>", "<b>2x</b>", "<b>3x</b>"]
    )
)

Which is pretty inconvenient because you have to specify the tickvals every time you want to do this.

So I was thinking that it could be a good idea to add something like:
fig.update_xaxis(tick_text_formatter=<function that formats a tick value>)

Thoughts?

Again, thanks for the awesome work!

從公開的入口 fig.update_layout 和 fig.update_xaxis 開始，接著追蹤 x 軸和 y 軸刻度標籤的表示方式。定義 formatter 的行為和 API，並考慮測試應如何驗證任意格式化，而不要求手動設定 tickvals 和 ticktext。