support texttemplate

[thomas-saigre]

For instance this figure

import plotly.express as px
df = px.data.tips()
fig = px.histogram(df, x="total_bill", y="tip", histfunc="avg", nbins=8, text_auto=True)
fig.show()

results is a figure with the following attirbute :
fig.data[0].texttemplate = '%{value}',
resulting in a display of the values in the plotly figure.

I have not yet looked into it, but I'm sure that texttemplate can do more than that !