Week Uptime plot points and x axis ticks alignment

Add note in documentation about how dates include time. If the tme is not `T00:00`, then the points will not align with the labels in the x axis.

Example with ponts aligned with ticks:
<img width="854" alt="imagen" src="https://github.com/inab/oeb-visualizations/assets/11412829/06bcc99c-5bd3-4b64-9ded-572397d63dde">

