Fix unicode font issues with matplotlib

[antoinecarme]

Following #76, PyAF plot contain empty boxes instead of unicode "characters".

[antoinecarme]

need t o find a way to force matplotlib to use a valid unicode font.

[antoinecarme]

https://github.com/matplotlib/matplotlib/pull/20740

[antoinecarme]

According to matplotlib issues wiht unicode, the default font families have to be defined before any kind of plotting.

the following code before building any pyaf model solves the unicode issues when plotting the time series (choose your favorite fonts, here are mine for chinese)

import matplotlib.pyplot as plt
plt.rcParams['font.family'] = ['Segoe UI Emoji', 'SimHei']

[antoinecarme]

[antoinecarme]

FIXED.